Checking if frame is complete and access duration doesn't need a decode

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

Index: Source/core/platform/image-decoders/gif/GIFImageDecoder.h
diff --git a/Source/core/platform/image-decoders/gif/GIFImageDecoder.h b/Source/core/platform/image-decoders/gif/GIFImageDecoder.h
index a4728d33a7368d77431bcc7e24d721877af2999e..8768fde7538a95ceef0e9658b0109931c8a3c448 100644
--- a/Source/core/platform/image-decoders/gif/GIFImageDecoder.h
+++ b/Source/core/platform/image-decoders/gif/GIFImageDecoder.h
@@ -49,6 +49,8 @@ namespace WebCore {
         virtual size_t frameCount();
         virtual int repetitionCount() const;
         virtual ImageFrame* frameBufferAtIndex(size_t index);
+        virtual bool frameIsCompleteAtIndex(size_t) const;
+        virtual float frameDurationAtIndex(size_t) const;
         // CAUTION: setFailed() deletes |m_reader|.  Be careful to avoid
         // accessing deleted memory, especially when calling this from inside
         // GIFImageReader!
@@ -72,6 +74,9 @@ namespace WebCore {
         // failure, this will mark the image as failed.
         bool initFrameBuffer(unsigned frameIndex);
 
+        // Return true only if the file is known to be truncated.
+        bool truncated() const;
+
         bool m_currentBufferSawAlpha;
         mutable int m_repetitionCount;
         OwnPtr<GIFImageReader> m_reader;