Add animation support for WebP images

Source/core/platform/image-decoders/ImageFrame.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2008, 2009 Google, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 134 matching lines @@
         m_bitmap->setDataComplete(); // Tell the bitmap it's done.
     }
 }
 
 void ImageFrame::reportMemoryUsage(MemoryObjectInfo* memoryObjectInfo) const
 {
     MemoryClassInfo info(memoryObjectInfo, this, PlatformMemoryTypes::Image);
     info.addMember(m_bitmap, "bitmap");
 }
 
+void ImageFrame::zeroFillFrameRect(const IntRect& rect)
+{
+    if (rect.isEmpty())
+        return;
+
+    // FIXME: Can we make this faster using Skia?
+    for (int y = rect.y(); y < rect.maxY(); ++y) {
+        uint8_t* const dst = reinterpret_cast<uint8_t*>(getAddr(rect.x(), rect.y()));
+        memset(dst, 0, (rect.maxX() - rect.x()) * sizeof(ImageFrame::PixelData));
+    }
+    setHasAlpha(true);
+}
+
 } // namespace WebCore