Add animation support for WebP images

Source/core/platform/image-decoders/ImageDecoder.h

Index: Source/core/platform/image-decoders/ImageDecoder.h
diff --git a/Source/core/platform/image-decoders/ImageDecoder.h b/Source/core/platform/image-decoders/ImageDecoder.h
index 83dbdc070a653ec942c629b7e635ae8c4f37560e..87e26acf590e488abe7bf1237afe507ba20a2359 100644
--- a/Source/core/platform/image-decoders/ImageDecoder.h
+++ b/Source/core/platform/image-decoders/ImageDecoder.h
@@ -194,10 +194,9 @@ namespace WebCore {
         RefPtr<NativeImageSkia> m_bitmap;
         SkBitmap::Allocator* m_allocator;
         bool m_hasAlpha;
-        IntRect m_originalFrameRect; // This will always just be the entire
-                                     // buffer except for GIF frames whose
-                                     // original rect was smaller than the
-                                     // overall image size.
+        // This will always just be the entire buffer except for GIF or WebP
+        // frames whose original rect was smaller than the overall image size.
+        IntRect m_originalFrameRect;
         FrameStatus m_status;
         unsigned m_duration;
         FrameDisposalMethod m_disposalMethod;
@@ -258,9 +257,9 @@ namespace WebCore {
 
         // This will only differ from size() for ICO (where each frame is a
         // different icon) or other formats where different frames are different
-        // sizes.  This does NOT differ from size() for GIF, since decoding GIFs
-        // composites any smaller frames against previous frames to create full-
-        // size frames.
+        // sizes. This does NOT differ from size() for GIF or WebP, since
+        // decoding GIF or WebP composites any smaller frames against previous
+        // frames to create full-size frames.
         virtual IntSize frameSizeAtIndex(size_t) const
         {
             return size();
@@ -372,8 +371,8 @@ namespace WebCore {
         bool failed() const { return m_failed; }
 
         // Clears decoded pixel data from before the provided frame unless that
-        // data may be needed to decode future frames (e.g. due to GIF frame
-        // compositing).
+        // data may be needed to decode future frames (e.g. due to GIF/WebP
+        // frame compositing).
         virtual void clearFrameBufferCache(size_t) { }
 
 #if ENABLE(IMAGE_DECODER_DOWN_SAMPLING)