Oilpan: ImageObserver needs to be a GC mixin.

third_party/WebKit/Source/platform/graphics/Image.h

 /*
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * 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 14 matching lines @@
  */
 
 #ifndef Image_h
 #define Image_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/Color.h"
 #include "platform/graphics/GraphicsTypes.h"
 #include "platform/graphics/ImageAnimationPolicy.h"
+#include "platform/graphics/ImageObserver.h"
 #include "platform/graphics/ImageOrientation.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "wtf/Assertions.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 #include "wtf/text/WTFString.h"
 
 class SkBitmap;
 class SkImage;
 
 namespace blink {
 
 class FloatPoint;
 class FloatRect;
 class FloatSize;
 class GraphicsContext;
 class Length;
 class SharedBuffer;
 class Image;
 
-// This class gets notified when an image creates or destroys decoded frames and when it advances animation frames.
-class ImageObserver;
-
 class PLATFORM_EXPORT Image : public RefCounted<Image> {
     friend class GeneratedImage;
     friend class CrossfadeGeneratedImage;
     friend class GradientGeneratedImage;
     friend class GraphicsContext;
     WTF_MAKE_NONCOPYABLE(Image);
 
 public:
     virtual ~Image();
 
@@ skipping 87 matching lines @@
 
 protected:
     Image(ImageObserver* = 0);
 
     void drawTiled(GraphicsContext&, const FloatRect& dstRect, const FloatPoint& srcPoint, const FloatSize& tileSize,
         SkXfermode::Mode, const FloatSize& repeatSpacing);
     void drawTiled(GraphicsContext&, const FloatRect& dstRect, const FloatRect& srcRect, const FloatSize& tileScaleFactor, TileRule hRule, TileRule vRule, SkXfermode::Mode);
 
 private:
     RefPtr<SharedBuffer> m_encodedImageData;
-    ImageObserver* m_imageObserver;
+    // TODO(Oilpan): consider having Image on the Oilpan heap and
+    // turn this into a Member<>.
+    //
+    // The observer (an ImageResource) is an untraced member, with the ImageResource
+    // being responsible of clearing itself out.
+    RawPtrWillBeUntracedMember<ImageObserver> m_imageObserver;
 };
 
 #define DEFINE_IMAGE_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName, Image, image, image->is##typeName(), image.is##typeName())
 
 } // namespace blink
 
 #endif