Decode GIF image frames on demand.

Source/core/platform/image-decoders/gif/GIFImageReader.h

Index: Source/core/platform/image-decoders/gif/GIFImageReader.h
diff --git a/Source/core/platform/image-decoders/gif/GIFImageReader.h b/Source/core/platform/image-decoders/gif/GIFImageReader.h
index 105cd655e692776bf219a260e57dd2e1ef61d0fa..aabf8c7350d6e99c7add741b54a1f12d424d4582 100644
--- a/Source/core/platform/image-decoders/gif/GIFImageReader.h
+++ b/Source/core/platform/image-decoders/gif/GIFImageReader.h
@@ -239,7 +239,7 @@ public:
         , m_globalColormapPosition(0)
         , m_globalColormapSize(0)
         , m_loopCount(cLoopCountNotSeen)
-        , m_currentDecodingFrame(0)
+        , m_decodedFramesCount(0)
         , m_parseCompleted(false)
     {
     }
@@ -249,8 +249,8 @@ public:
     }
 
     void setData(PassRefPtr<WebCore::SharedBuffer> data) { m_data = data; }
-    // FIXME: haltAtFrame should be size_t.
-    bool decode(WebCore::GIFImageDecoder::GIFQuery, unsigned haltAtFrame);
+    bool parse(WebCore::GIFImageDecoder::GIFParseQuery);
+    bool decode(const BitVector& frames);

[Alpha Left Google, 2013/05/18 00:39:35]

Why not just give the index? User of this API (GIFImageDecoder) can call this
multiple times.

[Xianzhu, 2013/05/20 04:30:59]

Done.

 
     size_t imagesCount() const
     {
@@ -290,7 +290,7 @@ public:
     bool parseCompleted() const { return m_parseCompleted; }
 
 private:
-    bool parse(size_t dataPosition, size_t len, bool parseSizeOnly);
+    bool parseData(size_t dataPosition, size_t len, WebCore::GIFImageDecoder::GIFParseQuery);
     void setRemainingBytes(size_t);
 
     const unsigned char* data(size_t dataPosition) const
@@ -322,7 +322,7 @@ private:
     int m_loopCount; // Netscape specific extension block to control the number of animation loops a GIF renders.
     
     Vector<OwnPtr<GIFFrameContext> > m_frames;
-    size_t m_currentDecodingFrame;
+    size_t m_decodedFramesCount;

[Alpha Left Google, 2013/05/18 00:39:35]

I don't think we need this any more. See my comments in GIFImageReader.cpp.

[Xianzhu, 2013/05/20 04:30:59]

Done.

 
     RefPtr<WebCore::SharedBuffer> m_data;
     bool m_parseCompleted;