add ImageGenerator::NewFromData to porting layer

BUG=skia:3275

Review URL: https://codereview.chromium.org/834633006
diff --git a/src/c/sk_surface.cpp b/src/c/sk_surface.cpp
index b605960..89b53d0 100644
--- a/src/c/sk_surface.cpp
+++ b/src/c/sk_surface.cpp
@@ -230,18 +230,8 @@
     return (sk_image_t*)SkImage::NewRasterCopy(info, pixels, rowBytes);
 }
 
-#include "SkDecodingImageGenerator.h"
-
 sk_image_t* sk_image_new_from_data(const sk_data_t* cdata) {
-    SkImageGenerator* gen = NULL;
-#if 0
-    // enable this when SkDecodingImageGenerator is available in chrome (decode codecs)
-    gen = SkDecodingImageGenerator::Create(AsData(cdata), SkDecodingImageGenerator::Options());
-#endif
-    if (NULL == gen) {
-        return NULL;
-    }
-    return ToImage(SkImage::NewFromGenerator(gen));
+    return ToImage(SkImage::NewFromData(AsData(cdata)));
 }
 
 sk_data_t* sk_image_encode(const sk_image_t* cimage) {
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index 8796b03..97e7475 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -7,6 +7,7 @@
 
 #include "SkBitmap.h"
 #include "SkCanvas.h"
+#include "SkImageGenerator.h"
 #include "SkImagePriv.h"
 #include "SkImage_Base.h"
 #include "SkReadPixelsRec.h"
@@ -72,6 +73,14 @@
     return NULL;
 }
 
+SkImage* SkImage::NewFromData(SkData* data) {
+    if (NULL == data) {
+        return NULL;
+    }
+    SkImageGenerator* generator = SkImageGenerator::NewFromData(data);
+    return generator ? SkImage::NewFromGenerator(generator) : NULL;
+}
+
 SkSurface* SkImage::newSurface(const SkImageInfo& info, const SkSurfaceProps* props) const {
     if (NULL == props) {
         props = &as_IB(this)->props();
diff --git a/src/image/SkImage_Raster.cpp b/src/image/SkImage_Raster.cpp
index 0ee3914..01a287b 100644
--- a/src/image/SkImage_Raster.cpp
+++ b/src/image/SkImage_Raster.cpp
@@ -10,7 +10,7 @@
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
-#include "SkDecodingImageGenerator.h"
+#include "SkImageGenerator.h"
 #include "SkSurface.h"
 
 class SkImage_Raster : public SkImage_Base {
diff --git a/src/lazy/SkDiscardablePixelRef.cpp b/src/lazy/SkDiscardablePixelRef.cpp
index 84152ed..4b7d47b 100644
--- a/src/lazy/SkDiscardablePixelRef.cpp
+++ b/src/lazy/SkDiscardablePixelRef.cpp
@@ -116,7 +116,13 @@
     return true;
 }
 
-// This is the public API
+// These are the public API
+
 bool SkInstallDiscardablePixelRef(SkImageGenerator* generator, SkBitmap* dst) {
     return SkInstallDiscardablePixelRef(generator, dst, NULL);
 }
+
+bool SkInstallDiscardablePixelRef(SkData* encoded, SkBitmap* dst) {
+    SkImageGenerator* generator = SkImageGenerator::NewFromData(encoded);
+    return generator ? SkInstallDiscardablePixelRef(generator, dst, NULL) : false;
+}
diff --git a/src/ports/SkImageGenerator_skia.cpp b/src/ports/SkImageGenerator_skia.cpp
new file mode 100644
index 0000000..cd02ae2
--- /dev/null
+++ b/src/ports/SkImageGenerator_skia.cpp
@@ -0,0 +1,116 @@
+/*
+ * Copyright 2015 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkData.h"
+#include "SkImageDecoder.h"
+#include "SkImageGenerator.h"
+#include "SkStream.h"
+
+class BareMemoryAllocator : public SkBitmap::Allocator {
+    const SkImageInfo   fInfo;
+    void* const         fMemory;
+    const size_t        fRowBytes;
+
+public:
+    BareMemoryAllocator(const SkImageInfo& info, void* memory, size_t rowBytes)
+        : fInfo(info), fMemory(memory), fRowBytes(rowBytes)
+    {}
+
+protected:
+    bool allocPixelRef(SkBitmap* bm, SkColorTable* ctable) SK_OVERRIDE {
+        const SkImageInfo bmi = bm->info();
+        if (bmi.width() != fInfo.width() || bmi.height() != fInfo.height() ||
+            bmi.colorType() != fInfo.colorType())
+        {
+            return false;
+        }
+        return bm->installPixels(bmi, fMemory, fRowBytes, ctable, NULL, NULL);
+    }
+};
+
+class SkImageDecoderGenerator : public SkImageGenerator {
+    const SkImageInfo               fInfo;
+    SkAutoTDelete<SkImageDecoder>   fDecoder;
+    SkAutoTUnref<SkData>            fData;
+
+public:
+    SkImageDecoderGenerator(const SkImageInfo& info, SkImageDecoder* decoder, SkData* data)
+        : fInfo(info), fDecoder(decoder), fData(SkRef(data))
+    {}
+
+protected:
+    SkData* onRefEncodedData() SK_OVERRIDE {
+        return SkRef(fData.get());
+    }
+
+    virtual bool onGetInfo(SkImageInfo* info) {
+        *info = fInfo;
+        return true;
+    }
+
+    virtual bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+                             SkPMColor ctableEntries[], int* ctableCount) {
+        SkMemoryStream stream(fData->data(), fData->size(), false);
+        SkAutoTUnref<BareMemoryAllocator> allocator(SkNEW_ARGS(BareMemoryAllocator,
+                                                               (info, pixels, rowBytes)));
+        fDecoder->setAllocator(allocator);
+        fDecoder->setRequireUnpremultipliedColors(kUnpremul_SkAlphaType == info.alphaType());
+
+        SkBitmap bm;
+        SkImageDecoder::Result result = fDecoder->decode(&stream, &bm, info.colorType(),
+                                                         SkImageDecoder::kDecodePixels_Mode);
+        switch (result) {
+            case SkImageDecoder::kSuccess:
+                break;
+            default:
+                return false;
+        }
+
+        SkASSERT(info.colorType() == bm.info().colorType());
+
+        if (kIndex_8_SkColorType == info.colorType()) {
+            SkASSERT(ctableEntries);
+
+            SkColorTable* ctable = bm.getColorTable();
+            if (NULL == ctable) {
+                return false;
+            }
+            const int count = ctable->count();
+            memcpy(ctableEntries, ctable->readColors(), count * sizeof(SkPMColor));
+            *ctableCount = count;
+        }
+        return true;
+    }
+
+    bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
+                         SkYUVColorSpace* colorSpace) SK_OVERRIDE {
+        SkMemoryStream stream(fData->data(), fData->size(), false);
+        return fDecoder->decodeYUV8Planes(&stream, sizes, planes, rowBytes, colorSpace);
+    }
+    
+};
+
+SkImageGenerator* SkImageGenerator::NewFromData(SkData* data) {
+    if (NULL == data) {
+        return NULL;
+    }
+
+    SkMemoryStream stream(data->data(), data->size(), false);
+    SkImageDecoder* decoder = SkImageDecoder::Factory(&stream);
+    if (NULL == decoder) {
+        return NULL;
+    }
+
+    SkBitmap bm;
+    stream.rewind();
+    if (!decoder->decode(&stream, &bm, kUnknown_SkColorType, SkImageDecoder::kDecodeBounds_Mode)) {
+        SkDELETE(decoder);
+        return NULL;
+    }
+
+    return SkNEW_ARGS(SkImageDecoderGenerator, (bm.info(), decoder, data));
+}
diff --git a/src/utils/SkLua.cpp b/src/utils/SkLua.cpp
index 2370b99..ba79933 100644
--- a/src/utils/SkLua.cpp
+++ b/src/utils/SkLua.cpp
@@ -14,7 +14,6 @@
 #include "SkBlurImageFilter.h"
 #include "SkCanvas.h"
 #include "SkData.h"
-#include "SkDecodingImageGenerator.h"
 #include "SkDocument.h"
 #include "SkGradientShader.h"
 #include "SkImage.h"
@@ -2008,9 +2007,7 @@
         const char* name = lua_tolstring(L, 1, NULL);
         SkAutoDataUnref data(SkData::NewFromFileName(name));
         if (data.get()) {
-            SkImage* image = SkImage::NewFromGenerator(
-                SkDecodingImageGenerator::Create(data, SkDecodingImageGenerator::Options()));
-
+            SkImage* image = SkImage::NewFromData(data);
             if (image) {
                 push_ref(L, image)->unref();
                 return 1;