Added API for Bevel NormalSource.

This CL adds an API  for Bevel normal source and a dummy implementation that returns a normal (0, 0, 1) every time.

This CL's base is the CL for accepting nullptrs: https://codereview.chromium.org/2132113002

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2080993002

Review-Url: https://codereview.chromium.org/2080993002
diff --git a/src/core/SkNormalBevelSource.cpp b/src/core/SkNormalBevelSource.cpp
new file mode 100644
index 0000000..feccb0c
--- /dev/null
+++ b/src/core/SkNormalBevelSource.cpp
@@ -0,0 +1,165 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkNormalBevelSource.h"
+
+#include "SkNormalSource.h"
+#include "SkPoint3.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrInvariantOutput.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "SkGr.h"
+
+class NormalBevelFP : public GrFragmentProcessor {
+public:
+    NormalBevelFP(SkNormalSource::BevelType type, SkScalar width, SkScalar height)
+        : fType(type)
+        , fWidth(width)
+        , fHeight(height) {
+        this->initClassID<NormalBevelFP>();
+    }
+
+    class GLSLNormalBevelFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLNormalBevelFP() {
+            fPrevWidth = SkFloatToScalar(0.0f);
+            fPrevHeight = SkFloatToScalar(0.0f);
+        }
+
+        void emitCode(EmitArgs& args) override {
+            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
+
+            const char* widthUniName = nullptr;
+            fWidthUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kFloat_GrSLType,
+                    kDefault_GrSLPrecision, "Width", &widthUniName);
+
+            const char* heightUniName = nullptr;
+            fHeightUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kFloat_GrSLType,
+                    kDefault_GrSLPrecision, "Height", &heightUniName);
+
+            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+        }
+
+        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
+                           GrProcessorKeyBuilder* b) {
+            const NormalBevelFP& fp = proc.cast<NormalBevelFP>();
+            b->add32(static_cast<int>(fp.fType));
+        }
+
+    protected:
+        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+            const NormalBevelFP& normalBevelFP = proc.cast<NormalBevelFP>();
+
+            if (fPrevWidth  != normalBevelFP.fWidth) {
+                pdman.set1f(fWidthUni, normalBevelFP.fWidth);
+                fPrevWidth = normalBevelFP.fWidth;
+            }
+            if (fPrevHeight != normalBevelFP.fHeight) {
+                pdman.set1f(fHeightUni, normalBevelFP.fHeight);
+                fPrevHeight = normalBevelFP.fHeight;
+            }
+        }
+
+    private:
+        SkScalar fPrevWidth;
+        GrGLSLProgramDataManager::UniformHandle fWidthUni;
+
+        SkScalar fPrevHeight;
+        GrGLSLProgramDataManager::UniformHandle fHeightUni;
+    };
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLNormalBevelFP::GenKey(*this, caps, b);
+    }
+
+    const char* name() const override { return "NormalBevelFP"; }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::ReadInput::kWillNot_ReadInput);
+    }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalBevelFP; }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        const NormalBevelFP& normalBevelFP = proc.cast<NormalBevelFP>();
+        return fType   == normalBevelFP.fType &&
+               fWidth  == normalBevelFP.fWidth &&
+               fHeight == normalBevelFP.fHeight;
+    }
+
+    SkNormalSource::BevelType fType;
+    SkScalar fWidth;
+    SkScalar fHeight;
+};
+
+sk_sp<GrFragmentProcessor> SkNormalBevelSourceImpl::asFragmentProcessor(
+        const SkShader::AsFPArgs&) const {
+
+    return sk_make_sp<NormalBevelFP>(fType, fWidth, fHeight);
+}
+
+#endif // SK_SUPPORT_GPU
+
+////////////////////////////////////////////////////////////////////////////
+
+SkNormalBevelSourceImpl::Provider::Provider() {}
+
+SkNormalBevelSourceImpl::Provider::~Provider() {}
+
+SkNormalSource::Provider* SkNormalBevelSourceImpl::asProvider(const SkShader::ContextRec &rec,
+                                                            void *storage) const {
+    return new (storage) Provider();
+}
+
+size_t SkNormalBevelSourceImpl::providerSize(const SkShader::ContextRec&) const {
+    return sizeof(Provider);
+}
+
+void SkNormalBevelSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
+                                                   int count) const {
+    for (int i = 0; i < count; i++) {
+        output[i] = {0.0f, 0.0f, 1.0f};
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> SkNormalBevelSourceImpl::CreateProc(SkReadBuffer& buf) {
+
+    auto type = static_cast<SkNormalSource::BevelType>(buf.readInt());
+    SkScalar width = buf.readScalar();
+    SkScalar height = buf.readScalar();
+
+    return sk_make_sp<SkNormalBevelSourceImpl>(type, width, height);
+}
+
+void SkNormalBevelSourceImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+
+    buf.writeInt(static_cast<int>(fType));
+    buf.writeScalar(fWidth);
+    buf.writeScalar(fHeight);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkNormalSource> SkNormalSource::MakeBevel(BevelType type, SkScalar width, SkScalar height) {
+    /* TODO make sure this checks are tolerant enough to account for loss of conversion when GPUs
+       use 16-bit float types. We don't want to assume stuff is non-zero on the GPU and be wrong.*/
+    SkASSERT(width > 0.0f && !SkScalarNearlyZero(width));
+    if (SkScalarNearlyZero(height)) {
+        return SkNormalSource::MakeFlat();
+    }
+
+    return sk_make_sp<SkNormalBevelSourceImpl>(type, width, height);
+}
diff --git a/src/core/SkNormalBevelSource.h b/src/core/SkNormalBevelSource.h
new file mode 100644
index 0000000..d133738
--- /dev/null
+++ b/src/core/SkNormalBevelSource.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalBevelSource_DEFINED
+#define SkNormalBevelSource_DEFINED
+
+#include "SkNormalSource.h"
+
+class SK_API SkNormalBevelSourceImpl : public SkNormalSource {
+public:
+    SkNormalBevelSourceImpl(BevelType type, SkScalar width, SkScalar height)
+        : fType(type)
+        , fWidth(width)
+        , fHeight(height) {}
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(const SkShader::AsFPArgs&) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
+                                         void* storage) const override;
+    size_t providerSize(const SkShader::ContextRec& rec) const override;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNormalBevelSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider();
+
+        virtual ~Provider();
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+
+    private:
+        typedef SkNormalSource::Provider INHERITED;
+
+    };
+
+    SkNormalSource::BevelType fType;
+    SkScalar fWidth;
+    SkScalar fHeight;
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+
+#endif
diff --git a/src/core/SkNormalFlatSource.cpp b/src/core/SkNormalFlatSource.cpp
new file mode 100644
index 0000000..fcb1a4f
--- /dev/null
+++ b/src/core/SkNormalFlatSource.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkNormalFlatSource.h"
+
+#include "SkNormalSource.h"
+#include "SkPoint3.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrInvariantOutput.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+
+class NormalFlatFP : public GrFragmentProcessor {
+public:
+    NormalFlatFP() {
+        this->initClassID<NormalFlatFP>();
+    }
+
+    class GLSLNormalFlatFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLNormalFlatFP() {}
+
+        void emitCode(EmitArgs& args) override {
+            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+
+            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+        }
+
+        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
+                           GrProcessorKeyBuilder* b) {
+            b->add32(0x0);
+        }
+
+    protected:
+        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {}
+    };
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLNormalFlatFP::GenKey(*this, caps, b);
+    }
+
+    const char* name() const override { return "NormalFlatFP"; }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::ReadInput::kWillNot_ReadInput);
+    }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalFlatFP; }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        return true;
+    }
+};
+
+sk_sp<GrFragmentProcessor> SkNormalFlatSourceImpl::asFragmentProcessor(
+        const SkShader::AsFPArgs&) const {
+
+    return sk_make_sp<NormalFlatFP>();
+}
+
+#endif // SK_SUPPORT_GPU
+
+////////////////////////////////////////////////////////////////////////////
+
+SkNormalFlatSourceImpl::Provider::Provider() {}
+
+SkNormalFlatSourceImpl::Provider::~Provider() {}
+
+SkNormalSource::Provider* SkNormalFlatSourceImpl::asProvider(const SkShader::ContextRec &rec,
+                                                           void *storage) const {
+    return new (storage) Provider();
+}
+
+size_t SkNormalFlatSourceImpl::providerSize(const SkShader::ContextRec&) const {
+    return sizeof(Provider);
+}
+
+void SkNormalFlatSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
+                                                  int count) const {
+    for (int i = 0; i < count; i++) {
+        output[i] = {0.0f, 0.0f, 1.0f};
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> SkNormalFlatSourceImpl::CreateProc(SkReadBuffer& buf) {
+    return sk_make_sp<SkNormalFlatSourceImpl>();
+}
+
+void SkNormalFlatSourceImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkNormalSource> SkNormalSource::MakeFlat() {
+    return sk_make_sp<SkNormalFlatSourceImpl>();
+}
diff --git a/src/core/SkNormalFlatSource.h b/src/core/SkNormalFlatSource.h
new file mode 100644
index 0000000..e129559
--- /dev/null
+++ b/src/core/SkNormalFlatSource.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalFlatSource_DEFINED
+#define SkNormalFlatSource_DEFINED
+
+#include "SkNormalSource.h"
+
+class SK_API SkNormalFlatSourceImpl : public SkNormalSource {
+public:
+    SkNormalFlatSourceImpl(){}
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(const SkShader::AsFPArgs&) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
+                                         void* storage) const override;
+    size_t providerSize(const SkShader::ContextRec& rec) const override;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNormalFlatSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider();
+
+        virtual ~Provider();
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+
+    private:
+        typedef SkNormalSource::Provider INHERITED;
+    };
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+#endif
diff --git a/src/core/SkNormalMapSource.cpp b/src/core/SkNormalMapSource.cpp
new file mode 100644
index 0000000..2ecf1d3
--- /dev/null
+++ b/src/core/SkNormalMapSource.cpp
@@ -0,0 +1,265 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkNormalMapSource.h"
+
+#include "SkLightingShader.h"
+#include "SkMatrix.h"
+#include "SkNormalSource.h"
+#include "SkPM4f.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrCoordTransform.h"
+#include "GrInvariantOutput.h"
+#include "GrTextureParams.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "SkGr.h"
+
+class NormalMapFP : public GrFragmentProcessor {
+public:
+    NormalMapFP(sk_sp<GrFragmentProcessor> mapFP, const SkMatrix& invCTM)
+        : fInvCTM(invCTM) {
+        this->registerChildProcessor(mapFP);
+
+        this->initClassID<NormalMapFP>();
+    }
+
+    class GLSLNormalMapFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLNormalMapFP()
+            : fColumnMajorInvCTM22{0.0f} {}
+
+        void emitCode(EmitArgs& args) override {
+            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
+
+            // add uniform
+            const char* xformUniName = nullptr;
+            fXformUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kMat22f_GrSLType,
+                                                   kDefault_GrSLPrecision, "Xform", &xformUniName);
+
+            SkString dstNormalColorName("dstNormalColor");
+            this->emitChild(0, nullptr, &dstNormalColorName, args);
+            fragBuilder->codeAppendf("vec3 normal = normalize(%s.rgb - vec3(0.5));",
+                                     dstNormalColorName.c_str());
+
+            // If there's no x & y components, return (0, 0, +/- 1) instead to avoid division by 0
+            fragBuilder->codeAppend( "if (abs(normal.z) > 0.999) {");
+            fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, normal.z, 0.0));",
+                    args.fOutputColor);
+            // Else, Normalizing the transformed X and Y, while keeping constant both Z and the
+            // vector's angle in the XY plane. This maintains the "slope" for the surface while
+            // appropriately rotating the normal regardless of any anisotropic scaling that occurs.
+            // Here, we call 'scaling factor' the number that must divide the transformed X and Y so
+            // that the normal's length remains equal to 1.
+            fragBuilder->codeAppend( "} else {");
+            fragBuilder->codeAppendf("    vec2 transformed = %s * normal.xy;",
+                    xformUniName);
+            fragBuilder->codeAppend( "    float scalingFactorSquared = "
+                                                 "( (transformed.x * transformed.x) "
+                                                   "+ (transformed.y * transformed.y) )"
+                                                 "/(1.0 - (normal.z * normal.z));");
+            fragBuilder->codeAppendf("    %s = vec4(transformed*inversesqrt(scalingFactorSquared),"
+                                                   "normal.z, 0.0);",
+                    args.fOutputColor);
+            fragBuilder->codeAppend( "}");
+        }
+
+        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
+                           GrProcessorKeyBuilder* b) {
+            b->add32(0x0);
+        }
+
+    protected:
+        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+            const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
+
+            const SkMatrix& invCTM = normalMapFP.invCTM();
+            fColumnMajorInvCTM22[0] = invCTM.get(SkMatrix::kMScaleX);
+            fColumnMajorInvCTM22[1] = invCTM.get(SkMatrix::kMSkewY);
+            fColumnMajorInvCTM22[2] = invCTM.get(SkMatrix::kMSkewX);
+            fColumnMajorInvCTM22[3] = invCTM.get(SkMatrix::kMScaleY);
+            pdman.setMatrix2f(fXformUni, fColumnMajorInvCTM22);
+        }
+
+    private:
+        float fColumnMajorInvCTM22[4];
+        GrGLSLProgramDataManager::UniformHandle fXformUni;
+    };
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLNormalMapFP::GenKey(*this, caps, b);
+    }
+
+    const char* name() const override { return "NormalMapFP"; }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::ReadInput::kWillNot_ReadInput);
+    }
+
+    const SkMatrix& invCTM() const { return fInvCTM; }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalMapFP; }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
+        return fInvCTM == normalMapFP.fInvCTM;
+    }
+
+    SkMatrix fInvCTM;
+};
+
+sk_sp<GrFragmentProcessor> SkNormalMapSourceImpl::asFragmentProcessor(
+        const SkShader::AsFPArgs& args) const {
+    sk_sp<GrFragmentProcessor> mapFP = fMapShader->asFragmentProcessor(args);
+    if (!mapFP) {
+        return nullptr;
+    }
+
+    return sk_make_sp<NormalMapFP>(std::move(mapFP), fInvCTM);
+}
+
+#endif // SK_SUPPORT_GPU
+
+////////////////////////////////////////////////////////////////////////////
+
+SkNormalMapSourceImpl::Provider::Provider(const SkNormalMapSourceImpl& source,
+                                        SkShader::Context* mapContext,
+                                        SkPaint* overridePaint)
+    : fSource(source)
+    , fMapContext(mapContext)
+    , fOverridePaint(overridePaint) {}
+
+SkNormalMapSourceImpl::Provider::~Provider() {
+    fMapContext->~Context();
+    fOverridePaint->~SkPaint();
+}
+
+SkNormalSource::Provider* SkNormalMapSourceImpl::asProvider(
+        const SkShader::ContextRec &rec, void *storage) const {
+    SkMatrix normTotalInv;
+    if (!this->computeNormTotalInverse(rec, &normTotalInv)) {
+        return nullptr;
+    }
+
+    // Overriding paint's alpha because we need the normal map's RGB channels to be unpremul'd
+    void* paintStorage = (char*)storage + sizeof(Provider);
+    SkPaint* overridePaint = new (paintStorage) SkPaint(*(rec.fPaint));
+    overridePaint->setAlpha(0xFF);
+    SkShader::ContextRec overrideRec(*overridePaint, *(rec.fMatrix), rec.fLocalMatrix,
+                                     rec.fPreferredDstType);
+
+    void* mapContextStorage = (char*) paintStorage + sizeof(SkPaint);
+    SkShader::Context* context = fMapShader->createContext(overrideRec, mapContextStorage);
+    if (!context) {
+        return nullptr;
+    }
+
+    return new (storage) Provider(*this, context, overridePaint);
+}
+
+size_t SkNormalMapSourceImpl::providerSize(const SkShader::ContextRec& rec) const {
+    return sizeof(Provider) + sizeof(SkPaint) + fMapShader->contextSize(rec);
+}
+
+bool SkNormalMapSourceImpl::computeNormTotalInverse(const SkShader::ContextRec& rec,
+                                                  SkMatrix* normTotalInverse) const {
+    SkMatrix total;
+    total.setConcat(*rec.fMatrix, fMapShader->getLocalMatrix());
+
+    const SkMatrix* m = &total;
+    if (rec.fLocalMatrix) {
+        total.setConcat(*m, *rec.fLocalMatrix);
+        m = &total;
+    }
+    return m->invert(normTotalInverse);
+}
+
+#define BUFFER_MAX 16
+void SkNormalMapSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
+                                                 int count) const {
+    SkPMColor tmpNormalColors[BUFFER_MAX];
+
+    do {
+        int n = SkTMin(count, BUFFER_MAX);
+
+        fMapContext->shadeSpan(x, y, tmpNormalColors, n);
+
+        for (int i = 0; i < n; i++) {
+            SkPoint3 tempNorm;
+
+            tempNorm.set(SkIntToScalar(SkGetPackedR32(tmpNormalColors[i])) - 127.0f,
+                         SkIntToScalar(SkGetPackedG32(tmpNormalColors[i])) - 127.0f,
+                         SkIntToScalar(SkGetPackedB32(tmpNormalColors[i])) - 127.0f);
+
+            tempNorm.normalize();
+
+
+            if (!SkScalarNearlyEqual(SkScalarAbs(tempNorm.fZ), 1.0f)) {
+                SkVector transformed = fSource.fInvCTM.mapVector(tempNorm.fX, tempNorm.fY);
+
+                // Normalizing the transformed X and Y, while keeping constant both Z and the
+                // vector's angle in the XY plane. This maintains the "slope" for the surface while
+                // appropriately rotating the normal for any anisotropic scaling that occurs.
+                // Here, we call scaling factor the number that must divide the transformed X and Y
+                // so that the normal's length remains equal to 1.
+                SkScalar scalingFactorSquared =
+                        (SkScalarSquare(transformed.fX) + SkScalarSquare(transformed.fY))
+                        / (1.0f - SkScalarSquare(tempNorm.fZ));
+                SkScalar invScalingFactor = SkScalarInvert(SkScalarSqrt(scalingFactorSquared));
+
+                output[i].fX = transformed.fX * invScalingFactor;
+                output[i].fY = transformed.fY * invScalingFactor;
+                output[i].fZ = tempNorm.fZ;
+            } else {
+                output[i] = {0.0f, 0.0f, tempNorm.fZ};
+                output[i].normalize();
+            }
+
+            SkASSERT(SkScalarNearlyEqual(output[i].length(), 1.0f));
+        }
+
+        output += n;
+        x += n;
+        count -= n;
+    } while (count > 0);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> SkNormalMapSourceImpl::CreateProc(SkReadBuffer& buf) {
+
+    sk_sp<SkShader> mapShader = buf.readFlattenable<SkShader>();
+
+    SkMatrix invCTM;
+    buf.readMatrix(&invCTM);
+
+    return sk_make_sp<SkNormalMapSourceImpl>(std::move(mapShader), invCTM);
+}
+
+void SkNormalMapSourceImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+
+    buf.writeFlattenable(fMapShader.get());
+    buf.writeMatrix(fInvCTM);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkNormalSource> SkNormalSource::MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm) {
+    SkMatrix invCTM;
+
+    if (!ctm.invert(&invCTM) || !map) {
+        return nullptr;
+    }
+
+    return sk_make_sp<SkNormalMapSourceImpl>(std::move(map), invCTM);
+}
diff --git a/src/core/SkNormalMapSource.h b/src/core/SkNormalMapSource.h
new file mode 100644
index 0000000..5908369
--- /dev/null
+++ b/src/core/SkNormalMapSource.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalMapSource_DEFINED
+#define SkNormalMapSource_DEFINED
+
+#include "SkNormalSource.h"
+
+class SkNormalMapSourceImpl : public SkNormalSource {
+public:
+    SkNormalMapSourceImpl(sk_sp<SkShader> mapShader, const SkMatrix& invCTM)
+            : fMapShader(std::move(mapShader))
+            , fInvCTM(invCTM) {}
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(const SkShader::AsFPArgs&) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
+                                         void* storage) const override;
+    size_t providerSize(const SkShader::ContextRec& rec) const override;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNormalMapSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+    bool computeNormTotalInverse(const SkShader::ContextRec& rec, SkMatrix* normTotalInverse) const;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider(const SkNormalMapSourceImpl& source, SkShader::Context* mapContext,
+                 SkPaint* overridePaint);
+
+        virtual ~Provider() override;
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+
+    private:
+        const SkNormalMapSourceImpl& fSource;
+        SkShader::Context* fMapContext;
+
+        SkPaint* fOverridePaint;
+
+        typedef SkNormalSource::Provider INHERITED;
+    };
+
+    sk_sp<SkShader> fMapShader;
+    SkMatrix        fInvCTM; // Inverse of the canvas total matrix, used for rotating normals.
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+#endif
+
diff --git a/src/core/SkNormalSource.cpp b/src/core/SkNormalSource.cpp
index 38cf0bf..2bea7ba 100644
--- a/src/core/SkNormalSource.cpp
+++ b/src/core/SkNormalSource.cpp
@@ -5,458 +5,20 @@
  * found in the LICENSE file.
  */
 
-#include "SkError.h"
-#include "SkErrorInternals.h"
-#include "SkLightingShader.h"
-#include "SkMatrix.h"
+#include "SkNormalBevelSource.h"
+#include "SkNormalFlatSource.h"
+#include "SkNormalMapSource.h"
 #include "SkNormalSource.h"
-#include "SkPM4f.h"
-#include "SkReadBuffer.h"
-#include "SkWriteBuffer.h"
 
-// Genretating vtable
+// Generating vtable
 SkNormalSource::~SkNormalSource() {}
 
-///////////////////////////////////////////////////////////////////////////////
-
-class NormalMapSourceImpl : public SkNormalSource {
-public:
-    NormalMapSourceImpl(sk_sp<SkShader> mapShader, const SkMatrix& invCTM)
-        : fMapShader(std::move(mapShader))
-        , fInvCTM(invCTM) {}
-
-#if SK_SUPPORT_GPU
-    sk_sp<GrFragmentProcessor> asFragmentProcessor(const SkShader::AsFPArgs&) const override;
-#endif
-
-    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
-                                                         void* storage) const override;
-
-    size_t providerSize(const SkShader::ContextRec& rec) const override;
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(NormalMapSourceImpl)
-
-protected:
-    void flatten(SkWriteBuffer& buf) const override;
-
-    bool computeNormTotalInverse(const SkShader::ContextRec& rec, SkMatrix* normTotalInverse) const;
-
-private:
-    class Provider : public SkNormalSource::Provider {
-    public:
-        Provider(const NormalMapSourceImpl& source, SkShader::Context* mapContext,
-                 SkPaint* overridePaint);
-
-        virtual ~Provider() override;
-
-        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
-
-    private:
-        const NormalMapSourceImpl& fSource;
-        SkShader::Context* fMapContext;
-
-        SkPaint* fOverridePaint;
-
-        typedef SkNormalSource::Provider INHERITED;
-    };
-
-    sk_sp<SkShader> fMapShader;
-    SkMatrix        fInvCTM; // Inverse of the canvas total matrix, used for rotating normals.
-
-    friend class SkNormalSource;
-
-    typedef SkNormalSource INHERITED;
-};
-
-////////////////////////////////////////////////////////////////////////////
-
-#if SK_SUPPORT_GPU
-
-#include "GrCoordTransform.h"
-#include "GrInvariantOutput.h"
-#include "GrTextureParams.h"
-#include "glsl/GrGLSLFragmentProcessor.h"
-#include "glsl/GrGLSLFragmentShaderBuilder.h"
-#include "SkGr.h"
-
-class NormalMapFP : public GrFragmentProcessor {
-public:
-    NormalMapFP(sk_sp<GrFragmentProcessor> mapFP, const SkMatrix& invCTM)
-        : fInvCTM(invCTM) {
-        this->registerChildProcessor(mapFP);
-
-        this->initClassID<NormalMapFP>();
-    }
-
-    class GLSLNormalMapFP : public GrGLSLFragmentProcessor {
-    public:
-        GLSLNormalMapFP()
-            : fColumnMajorInvCTM22{0.0f} {}
-
-        void emitCode(EmitArgs& args) override {
-            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
-            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
-
-            // add uniform
-            const char* xformUniName = nullptr;
-            fXformUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kMat22f_GrSLType,
-                                                   kDefault_GrSLPrecision, "Xform", &xformUniName);
-
-            SkString dstNormalColorName("dstNormalColor");
-            this->emitChild(0, nullptr, &dstNormalColorName, args);
-            fragBuilder->codeAppendf("vec3 normal = normalize(%s.rgb - vec3(0.5));",
-                                     dstNormalColorName.c_str());
-
-            // If there's no x & y components, return (0, 0, +/- 1) instead to avoid division by 0
-            fragBuilder->codeAppend( "if (abs(normal.z) > 0.999) {");
-            fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, normal.z, 0.0));",
-                    args.fOutputColor);
-            // Else, Normalizing the transformed X and Y, while keeping constant both Z and the
-            // vector's angle in the XY plane. This maintains the "slope" for the surface while
-            // appropriately rotating the normal regardless of any anisotropic scaling that occurs.
-            // Here, we call 'scaling factor' the number that must divide the transformed X and Y so
-            // that the normal's length remains equal to 1.
-            fragBuilder->codeAppend( "} else {");
-            fragBuilder->codeAppendf("    vec2 transformed = %s * normal.xy;",
-                    xformUniName);
-            fragBuilder->codeAppend( "    float scalingFactorSquared = "
-                                                 "( (transformed.x * transformed.x) "
-                                                   "+ (transformed.y * transformed.y) )"
-                                                 "/(1.0 - (normal.z * normal.z));");
-            fragBuilder->codeAppendf("    %s = vec4(transformed*inversesqrt(scalingFactorSquared),"
-                                                   "normal.z, 0.0);",
-                    args.fOutputColor);
-            fragBuilder->codeAppend( "}");
-        }
-
-        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
-                           GrProcessorKeyBuilder* b) {
-            b->add32(0x0);
-        }
-
-    protected:
-        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
-            const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
-
-            const SkMatrix& invCTM = normalMapFP.invCTM();
-            fColumnMajorInvCTM22[0] = invCTM.get(SkMatrix::kMScaleX);
-            fColumnMajorInvCTM22[1] = invCTM.get(SkMatrix::kMSkewY);
-            fColumnMajorInvCTM22[2] = invCTM.get(SkMatrix::kMSkewX);
-            fColumnMajorInvCTM22[3] = invCTM.get(SkMatrix::kMScaleY);
-            pdman.setMatrix2f(fXformUni, fColumnMajorInvCTM22);
-        }
-
-    private:
-        float fColumnMajorInvCTM22[4];
-        GrGLSLProgramDataManager::UniformHandle fXformUni;
-    };
-
-    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
-        GLSLNormalMapFP::GenKey(*this, caps, b);
-    }
-
-    const char* name() const override { return "NormalMapFP"; }
-
-    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
-        inout->setToUnknown(GrInvariantOutput::ReadInput::kWillNot_ReadInput);
-    }
-
-    const SkMatrix& invCTM() const { return fInvCTM; }
-
-private:
-    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalMapFP; }
-
-    bool onIsEqual(const GrFragmentProcessor& proc) const override {
-        const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
-        return fInvCTM == normalMapFP.fInvCTM;
-    }
-
-    SkMatrix fInvCTM;
-};
-
-sk_sp<GrFragmentProcessor> NormalMapSourceImpl::asFragmentProcessor(
-        const SkShader::AsFPArgs& args) const {
-    sk_sp<GrFragmentProcessor> mapFP = fMapShader->asFragmentProcessor(args);
-    if (!mapFP) {
-        return nullptr;
-    }
-
-    return sk_make_sp<NormalMapFP>(std::move(mapFP), fInvCTM);
-}
-
-#endif // SK_SUPPORT_GPU
-
-////////////////////////////////////////////////////////////////////////////
-
-NormalMapSourceImpl::Provider::Provider(const NormalMapSourceImpl& source,
-                                        SkShader::Context* mapContext,
-                                        SkPaint* overridePaint)
-    : fSource(source)
-    , fMapContext(mapContext)
-    , fOverridePaint(overridePaint) {}
-
-NormalMapSourceImpl::Provider::~Provider() {
-    fMapContext->~Context();
-    fOverridePaint->~SkPaint();
-}
-
-SkNormalSource::Provider* NormalMapSourceImpl::asProvider(
-        const SkShader::ContextRec &rec, void *storage) const {
-    SkMatrix normTotalInv;
-    if (!this->computeNormTotalInverse(rec, &normTotalInv)) {
-        return nullptr;
-    }
-
-    // Overriding paint's alpha because we need the normal map's RGB channels to be unpremul'd
-    void* paintStorage = (char*)storage + sizeof(Provider);
-    SkPaint* overridePaint = new (paintStorage) SkPaint(*(rec.fPaint));
-    overridePaint->setAlpha(0xFF);
-    SkShader::ContextRec overrideRec(*overridePaint, *(rec.fMatrix), rec.fLocalMatrix,
-                                     rec.fPreferredDstType);
-
-    void* mapContextStorage = (char*) paintStorage + sizeof(SkPaint);
-    SkShader::Context* context = fMapShader->createContext(overrideRec, mapContextStorage);
-    if (!context) {
-        return nullptr;
-    }
-
-    return new (storage) Provider(*this, context, overridePaint);
-}
-
-size_t NormalMapSourceImpl::providerSize(const SkShader::ContextRec& rec) const {
-    return sizeof(Provider) + sizeof(SkPaint) + fMapShader->contextSize(rec);
-}
-
-bool NormalMapSourceImpl::computeNormTotalInverse(const SkShader::ContextRec& rec,
-                                                  SkMatrix* normTotalInverse) const {
-    SkMatrix total;
-    total.setConcat(*rec.fMatrix, fMapShader->getLocalMatrix());
-
-    const SkMatrix* m = &total;
-    if (rec.fLocalMatrix) {
-        total.setConcat(*m, *rec.fLocalMatrix);
-        m = &total;
-    }
-    return m->invert(normTotalInverse);
-}
-
-#define BUFFER_MAX 16
-void NormalMapSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
-                                                 int count) const {
-    SkPMColor tmpNormalColors[BUFFER_MAX];
-
-    do {
-        int n = SkTMin(count, BUFFER_MAX);
-
-        fMapContext->shadeSpan(x, y, tmpNormalColors, n);
-
-        for (int i = 0; i < n; i++) {
-            SkPoint3 tempNorm;
-
-            tempNorm.set(SkIntToScalar(SkGetPackedR32(tmpNormalColors[i])) - 127.0f,
-                         SkIntToScalar(SkGetPackedG32(tmpNormalColors[i])) - 127.0f,
-                         SkIntToScalar(SkGetPackedB32(tmpNormalColors[i])) - 127.0f);
-
-            tempNorm.normalize();
-
-
-            if (!SkScalarNearlyEqual(SkScalarAbs(tempNorm.fZ), 1.0f)) {
-                SkVector transformed = fSource.fInvCTM.mapVector(tempNorm.fX, tempNorm.fY);
-
-                // Normalizing the transformed X and Y, while keeping constant both Z and the
-                // vector's angle in the XY plane. This maintains the "slope" for the surface while
-                // appropriately rotating the normal for any anisotropic scaling that occurs.
-                // Here, we call scaling factor the number that must divide the transformed X and Y
-                // so that the normal's length remains equal to 1.
-                SkScalar scalingFactorSquared =
-                        (SkScalarSquare(transformed.fX) + SkScalarSquare(transformed.fY))
-                        / (1.0f - SkScalarSquare(tempNorm.fZ));
-                SkScalar invScalingFactor = SkScalarInvert(SkScalarSqrt(scalingFactorSquared));
-
-                output[i].fX = transformed.fX * invScalingFactor;
-                output[i].fY = transformed.fY * invScalingFactor;
-                output[i].fZ = tempNorm.fZ;
-            } else {
-                output[i] = {0.0f, 0.0f, tempNorm.fZ};
-                output[i].normalize();
-            }
-
-            SkASSERT(SkScalarNearlyEqual(output[i].length(), 1.0f));
-        }
-
-        output += n;
-        x += n;
-        count -= n;
-    } while (count > 0);
-}
-
-////////////////////////////////////////////////////////////////////////////////
-
-sk_sp<SkFlattenable> NormalMapSourceImpl::CreateProc(SkReadBuffer& buf) {
-
-    sk_sp<SkShader> mapShader = buf.readFlattenable<SkShader>();
-
-    SkMatrix invCTM;
-    buf.readMatrix(&invCTM);
-
-    return sk_make_sp<NormalMapSourceImpl>(std::move(mapShader), invCTM);
-}
-
-void NormalMapSourceImpl::flatten(SkWriteBuffer& buf) const {
-    this->INHERITED::flatten(buf);
-
-    buf.writeFlattenable(fMapShader.get());
-    buf.writeMatrix(fInvCTM);
-}
-
-////////////////////////////////////////////////////////////////////////////
-
-sk_sp<SkNormalSource> SkNormalSource::MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm) {
-    SkMatrix invCTM;
-
-    if (!ctm.invert(&invCTM) || !map) {
-        return nullptr;
-    }
-
-    return sk_make_sp<NormalMapSourceImpl>(std::move(map), invCTM);
-}
-
-///////////////////////////////////////////////////////////////////////////////
-
-class SK_API NormalFlatSourceImpl : public SkNormalSource {
-public:
-    NormalFlatSourceImpl(){}
-
-#if SK_SUPPORT_GPU
-    sk_sp<GrFragmentProcessor> asFragmentProcessor(const SkShader::AsFPArgs&) const override;
-#endif
-
-    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
-                                         void* storage) const override;
-    size_t providerSize(const SkShader::ContextRec& rec) const override;
-
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(NormalFlatSourceImpl)
-
-protected:
-    void flatten(SkWriteBuffer& buf) const override;
-
-private:
-    class Provider : public SkNormalSource::Provider {
-    public:
-        Provider();
-
-        virtual ~Provider();
-
-        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
-
-    private:
-        typedef SkNormalSource::Provider INHERITED;
-    };
-
-    friend class SkNormalSource;
-
-    typedef SkNormalSource INHERITED;
-};
-
-////////////////////////////////////////////////////////////////////////////
-
-#if SK_SUPPORT_GPU
-
-class NormalFlatFP : public GrFragmentProcessor {
-public:
-    NormalFlatFP() {
-        this->initClassID<NormalFlatFP>();
-    }
-
-    class GLSLNormalFlatFP : public GrGLSLFragmentProcessor {
-    public:
-        GLSLNormalFlatFP() {}
-
-        void emitCode(EmitArgs& args) override {
-            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
-
-            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
-        }
-
-        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
-                           GrProcessorKeyBuilder* b) {
-            b->add32(0x0);
-        }
-
-    protected:
-        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {}
-    };
-
-    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
-        GLSLNormalFlatFP::GenKey(*this, caps, b);
-    }
-
-    const char* name() const override { return "NormalFlatFP"; }
-
-    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
-        inout->setToUnknown(GrInvariantOutput::ReadInput::kWillNot_ReadInput);
-    }
-
-private:
-    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalFlatFP; }
-
-    bool onIsEqual(const GrFragmentProcessor& proc) const override {
-        return true;
-    }
-};
-
-sk_sp<GrFragmentProcessor> NormalFlatSourceImpl::asFragmentProcessor(
-        const SkShader::AsFPArgs&) const {
-
-    return sk_make_sp<NormalFlatFP>();
-}
-
-#endif // SK_SUPPORT_GPU
-
-////////////////////////////////////////////////////////////////////////////
-
-NormalFlatSourceImpl::Provider::Provider() {}
-
-NormalFlatSourceImpl::Provider::~Provider() {}
-
-SkNormalSource::Provider* NormalFlatSourceImpl::asProvider(const SkShader::ContextRec &rec,
-                                                           void *storage) const {
-    return new (storage) Provider();
-}
-
-size_t NormalFlatSourceImpl::providerSize(const SkShader::ContextRec&) const {
-    return sizeof(Provider);
-}
-
-void NormalFlatSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
-                                                  int count) const {
-    for (int i = 0; i < count; i++) {
-        output[i] = {0.0f, 0.0f, 1.0f};
-    }
-}
-
-////////////////////////////////////////////////////////////////////////////////
-
-sk_sp<SkFlattenable> NormalFlatSourceImpl::CreateProc(SkReadBuffer& buf) {
-    return sk_make_sp<NormalFlatSourceImpl>();
-}
-
-void NormalFlatSourceImpl::flatten(SkWriteBuffer& buf) const {
-    this->INHERITED::flatten(buf);
-}
-
-////////////////////////////////////////////////////////////////////////////
-
-sk_sp<SkNormalSource> SkNormalSource::MakeFlat() {
-    return sk_make_sp<NormalFlatSourceImpl>();
-}
-
-////////////////////////////////////////////////////////////////////////////
-
 ////////////////////////////////////////////////////////////////////////////
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkNormalSource)
-    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(NormalMapSourceImpl)
-    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(NormalFlatSourceImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNormalMapSourceImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNormalFlatSourceImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNormalBevelSourceImpl)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ////////////////////////////////////////////////////////////////////////////
diff --git a/src/core/SkNormalSource.h b/src/core/SkNormalSource.h
index f8db496..8cbb3e4 100644
--- a/src/core/SkNormalSource.h
+++ b/src/core/SkNormalSource.h
@@ -9,6 +9,14 @@
 #define SkNormalSource_DEFINED
 
 #include "SkFlattenable.h"
+#include "SkShader.h"
+
+class SkMatrix;
+struct SkPoint3;
+
+#if SK_SUPPORT_GPU
+class GrFragmentProcessor;
+#endif
 
 /** Abstract class that generates or reads in normals for use by SkLightingShader.
 */
@@ -64,6 +72,52 @@
     */
     static sk_sp<SkNormalSource> MakeFlat();
 
+    /** This enum specifies the shape of the bevel. All bevels output <0, 0, 1> as the surface
+     *  normal for any point more than 'width' away from any edge.
+     *
+     *  Mathematical details:
+     *  For the purpose of describing the shape of the bevel, we define 'w' to be the given width of
+     *  the bevel, and 'h' to be the given height. We will assume the shape is rotated such that the
+     *  point being shaded as well as the closest point in the shape's edge to that point are in the
+     *  x-axis, and the shape is translated so that the aforementioned point in the edge is at
+     *  coordinates (w, 0, 0) and the end of the bevel is at (0, 0, h).
+     *
+     */
+    enum class BevelType {
+        /* This bevel simulates a surface that is slanted from the shape's edges inwards, linearly.
+         *
+         * Mathematical details:
+         * This bevel follows a straight line from (w, 0, 0) to (0, 0, h).
+         */
+        kLinear,
+        /* This bevel simulates a surface that rounds off at the shape's edges, smoothly becoming
+         * perpendicular to the x-y plane.
+         *
+         * Mathematical details:
+         * This bevel follows the only quadratic bezier curve whose start point is at (w, 0, 0),
+         * control point is at (w, 0, h), and end point is at (0, 0, h).
+         */
+        kRoundedOut,
+        /* This bevel simulates a surface that sharply becomes perpendicular to the x-y plane when
+         * at 'width' units from the nearest edge, and then rounds off towards the shape's
+         * edge, smoothly becoming parallel to the x-y plane.
+         *
+         * Mathematical details:
+         * This bevel follows the only quadratic bezier curve whose start point is at (w, 0, 0),
+         * control point is at (0, 0, 0), and end point is at (0, 0, h).
+         */
+        kRoundedIn
+    };
+    /** Returns a normal source that generates a bevel for the given shape. UNIMPLEMENTED: Will
+        return straight-up normals only.
+
+        @param  type   the type of bevel to add
+        @param  width  the width of the bevel, in source space. Must be positive.
+        @param  height the height of the plateau, in source space. Can be positive, negative,
+                       or zero. A negative height means the simulated bevels slope downwards.
+    */
+    static sk_sp<SkNormalSource> MakeBevel(BevelType, SkScalar width, SkScalar height);
+
     SK_DEFINE_FLATTENABLE_TYPE(SkNormalSource)
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 };