GIF decoding to Index8, unit tests and misusing unit test as benchmark

third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h

Index: third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
index 3ce2da9d3bbc71324c81ccc2e0559ece8a61b519..fbdc93a6414b4966edee0488e4c6e7c9d52878b8 100644
--- a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
+++ b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
@@ -31,6 +31,7 @@
 #include "wtf/OwnPtr.h"
 
 class GIFImageReader;
+struct GIFFrameContext;
 
 typedef Vector<unsigned char> GIFRow;
 
@@ -40,7 +41,7 @@ namespace blink {
 class PLATFORM_EXPORT GIFImageDecoder final : public ImageDecoder {
     WTF_MAKE_NONCOPYABLE(GIFImageDecoder);
 public:
-    GIFImageDecoder(AlphaOption, GammaAndColorProfileOption, size_t maxDecodedBytes);
+    GIFImageDecoder(AlphaOption, GammaAndColorProfileOption, size_t maxDecodedBytes, ImageFrame::ColorType decodeTo = ImageFrame::Index8);
     ~GIFImageDecoder() override;
 
     enum GIFParseQuery { GIFSizeQuery, GIFFrameCountQuery };
@@ -58,12 +59,31 @@ public:
     bool setFailed() override;
 
     // Callbacks from the GIF reader.
-    bool haveDecodedRow(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
+    bool (GIFImageDecoder::*phaveDecodedRow)(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
+    inline bool haveDecodedRow(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
+    {
+        return (this->*phaveDecodedRow)(frameIndex, rowBegin, width, rowNumber, repeatCount, writeTransparentPixels);
+    }
     bool frameComplete(size_t frameIndex);
 
+    // Called to initialize the frame buffer with the given index, based on
+    // the previous frame's disposal method. Returns true on success. On
+    // failure, this will mark the image as failed.
+    bool initFrameBuffer(size_t frameIndex);
+
+    // Callback implementations for different output.
+    bool haveDecodedRowN32(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
+    bool haveDecodedRowIndex8(size_t frameIndex, GIFRow::const_iterator rowBegin, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
+
+    // Callback when reader detects state requiring RGBA decoding.
+    void setForceN32Decoding(bool);
+
     // For testing.
     bool parseCompleted() const;
 
+    // For supporting both N32 and Index8 output.
+    bool canDecodeTo(size_t index, ImageFrame::ColorType outputType) override;
+
 private:
     // ImageDecoder:
     void clearFrameBuffer(size_t frameIndex) override;
@@ -72,18 +92,26 @@ private:
     void initializeNewFrame(size_t) override;
     void decode(size_t) override;
 
+
     // Parses as much as is needed to answer the query, ignoring bitmap
     // data. If parsing fails, sets the "decode failure" flag.
     void parse(GIFParseQuery);
 
-    // Called to initialize the frame buffer with the given index, based on
-    // the previous frame's disposal method. Returns true on success. On
-    // failure, this will mark the image as failed.
-    bool initFrameBuffer(size_t frameIndex);
+    bool initFrameBufferN32(size_t frameIndex);
+
+    void updateRequiredPreviousFrame(ImageFrame*, const GIFFrameContext&);
 
     bool m_currentBufferSawAlpha;
     mutable int m_repetitionCount;
     OwnPtr<GIFImageReader> m_reader;
+
+    // Holds information about which decoding output was requested in constructor.
+    // N32 color mode is used for testing only.
+    ImageFrame::ColorType m_colorMode;
+
+    // Used in Index8 decoding mode, some of the frames need to get decoded to N32.
+    // This flag is reset when situation allows going back to Index8 decoding in initFrameBuffer.
+    bool m_forceN32Decoding;
 };
 
 } // namespace blink