Reland "Base Gradient FP Refactor"

This reverts commit 1ea5656a285bcfef445d6f69eaab477e68595b54.

Reason for revert: Fixed google3 build failure

Original change's description:
> Revert "Base Gradient FP Refactor"
> 
> This reverts commit 10f7a1e07554a362aef979d32ba288a009bdff90.
> 
> Reason for revert: broke google3 roll
> Original change's description:
> > Base Gradient FP Refactor
> > 
> > --
> > 
> > Redefines how gradients will be written in the GPU back-end:
> > 
> > They are split into three fragment processor components: master, layout, and colorizer.
> > The layout FP is responsible for converting the fragment position into an interpolant value, t.
> > Each high-level gradient--such as linear, radial, etc.--are implemented solely in a layout FP.
> > The colorizer FP is responsible for converting t into a color.
> > The master FP invokes the layout, clamps t into the proper domain, and then invokes the colorizer.
> > GrGradientShader provides factory functions to create FP graphs from SkGradientShader instances.
> > This pattern is documented in gpu/gradients/README.md.
> > 
> > Goals for current CL
> > ====================
> > 
> > Outline the FP components by providing .fp implementations for the simplest gradients.
> > Defines a two-color single interval colorizer and a linear gradient layout, and the master effect.
> > A MakeLinear() factory function is provided that can convert SkGradientShaders that fit these constraints.
> > SkLinearGradient first attempts to use the new system, falling back to the original GrGradientEffect.
> > 
> > Future CLs
> > ==========
> > 
> > To keep the CL reviews manageable, additional dependent CLs will be added that gradually replace past functionality.
> > A CL for each layout will be defined.
> > CLs for the different analytic colorizer cases and the textured gradient case will be defined.
> > Once the new system supports all current layouts and colorizer capabilities, all old GPU gradient code will be removed.
> > After this clean-up, analytic colorization can hopefully be expanded to reduce the usage of textured gradients.
> > 
> > Bug: skia:
> > Change-Id: Iafe7b8b4071491a71c473babcd7bedda659150c1
> > Reviewed-on: https://skia-review.googlesource.com/148120
> > Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> > Reviewed-by: Brian Salomon <bsalomon@google.com>
> 
> TBR=bsalomon@google.com,michaelludwig@google.com
> 
> Change-Id: Ib735e323795ac8874cb00b007a915786b50517a6
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:
> Reviewed-on: https://skia-review.googlesource.com/153600
> Reviewed-by: Cary Clark <caryclark@google.com>
> Commit-Queue: Cary Clark <caryclark@google.com>

TBR=bsalomon@google.com,caryclark@google.com,michaelludwig@google.com

Change-Id: Ibf6ffbcb1af0dfbdac7317151aeb08f18f84c7fd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/153887
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
diff --git a/src/gpu/gradients/GrClampedGradientEffect.cpp b/src/gpu/gradients/GrClampedGradientEffect.cpp
new file mode 100644
index 0000000..4c8b3a1
--- /dev/null
+++ b/src/gpu/gradients/GrClampedGradientEffect.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/**************************************************************************************************
+ *** This file was autogenerated from GrClampedGradientEffect.fp; do not modify.
+ **************************************************************************************************/
+#include "GrClampedGradientEffect.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLProgramBuilder.h"
+#include "GrTexture.h"
+#include "SkSLCPP.h"
+#include "SkSLUtil.h"
+class GrGLSLClampedGradientEffect : public GrGLSLFragmentProcessor {
+public:
+    GrGLSLClampedGradientEffect() {}
+    void emitCode(EmitArgs& args) override {
+        GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+        const GrClampedGradientEffect& _outer = args.fFp.cast<GrClampedGradientEffect>();
+        (void)_outer;
+        auto leftBorderColor = _outer.leftBorderColor();
+        (void)leftBorderColor;
+        auto rightBorderColor = _outer.rightBorderColor();
+        (void)rightBorderColor;
+        fLeftBorderColorVar = args.fUniformHandler->addUniform(
+                kFragment_GrShaderFlag, kHalf4_GrSLType, kDefault_GrSLPrecision, "leftBorderColor");
+        fRightBorderColorVar =
+                args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kHalf4_GrSLType,
+                                                 kDefault_GrSLPrecision, "rightBorderColor");
+        SkString _child1("_child1");
+        this->emitChild(1, &_child1, args);
+        fragBuilder->codeAppendf(
+                "half4 t = %s;\nif (t.x < 0.0) {\n    %s = %s;\n} else if (float(t.x) > 1.0) {\n   "
+                " %s = %s;\n} else {",
+                _child1.c_str(), args.fOutputColor,
+                args.fUniformHandler->getUniformCStr(fLeftBorderColorVar), args.fOutputColor,
+                args.fUniformHandler->getUniformCStr(fRightBorderColorVar));
+        SkString _input0("t");
+        SkString _child0("_child0");
+        this->emitChild(0, _input0.c_str(), &_child0, args);
+        fragBuilder->codeAppendf("\n    %s = %s;\n}\n", args.fOutputColor, _child0.c_str());
+    }
+
+private:
+    void onSetData(const GrGLSLProgramDataManager& pdman,
+                   const GrFragmentProcessor& _proc) override {
+        const GrClampedGradientEffect& _outer = _proc.cast<GrClampedGradientEffect>();
+        {
+            const GrColor4f& leftBorderColorValue = _outer.leftBorderColor();
+            if (fLeftBorderColorPrev != leftBorderColorValue) {
+                fLeftBorderColorPrev = leftBorderColorValue;
+                pdman.set4fv(fLeftBorderColorVar, 1, leftBorderColorValue.fRGBA);
+            }
+            const GrColor4f& rightBorderColorValue = _outer.rightBorderColor();
+            if (fRightBorderColorPrev != rightBorderColorValue) {
+                fRightBorderColorPrev = rightBorderColorValue;
+                pdman.set4fv(fRightBorderColorVar, 1, rightBorderColorValue.fRGBA);
+            }
+        }
+    }
+    GrColor4f fLeftBorderColorPrev = GrColor4f::kIllegalConstructor;
+    GrColor4f fRightBorderColorPrev = GrColor4f::kIllegalConstructor;
+    UniformHandle fLeftBorderColorVar;
+    UniformHandle fRightBorderColorVar;
+};
+GrGLSLFragmentProcessor* GrClampedGradientEffect::onCreateGLSLInstance() const {
+    return new GrGLSLClampedGradientEffect();
+}
+void GrClampedGradientEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
+                                                    GrProcessorKeyBuilder* b) const {}
+bool GrClampedGradientEffect::onIsEqual(const GrFragmentProcessor& other) const {
+    const GrClampedGradientEffect& that = other.cast<GrClampedGradientEffect>();
+    (void)that;
+    if (fLeftBorderColor != that.fLeftBorderColor) return false;
+    if (fRightBorderColor != that.fRightBorderColor) return false;
+    return true;
+}
+GrClampedGradientEffect::GrClampedGradientEffect(const GrClampedGradientEffect& src)
+        : INHERITED(kGrClampedGradientEffect_ClassID, src.optimizationFlags())
+        , fLeftBorderColor(src.fLeftBorderColor)
+        , fRightBorderColor(src.fRightBorderColor) {
+    this->registerChildProcessor(src.childProcessor(0).clone());
+    this->registerChildProcessor(src.childProcessor(1).clone());
+}
+std::unique_ptr<GrFragmentProcessor> GrClampedGradientEffect::clone() const {
+    return std::unique_ptr<GrFragmentProcessor>(new GrClampedGradientEffect(*this));
+}