Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/loader/ImageLoader.h

Index: Source/core/loader/ImageLoader.h
diff --git a/Source/core/loader/ImageLoader.h b/Source/core/loader/ImageLoader.h
index f06089e2e5ae62f7eea6a4e8c991302d79b64284..92f450981942022964f173f91a189da70e25b2d3 100644
--- a/Source/core/loader/ImageLoader.h
+++ b/Source/core/loader/ImageLoader.h
@@ -26,10 +26,19 @@
 #include "core/loader/cache/CachedImage.h"
 #include "core/loader/cache/CachedImageClient.h"
 #include "core/loader/cache/CachedResourceHandle.h"
+#include "wtf/HashSet.h"
 #include "wtf/text/AtomicString.h"
 
 namespace WebCore {
 
+class ImageLoaderClient {
+public:
+    virtual void notifyImageSourceChanged() { }
+
+protected:
+    ImageLoaderClient() { }
+};
+
 class Element;
 class ImageLoader;
 class RenderImageResource;
@@ -69,6 +78,9 @@ public:
     static void dispatchPendingLoadEvents();
     static void dispatchPendingErrorEvents();
 
+    void addClient(ImageLoaderClient* client) { m_clients.add(client); }
+    void removeClient(ImageLoaderClient* client) { m_clients.remove(client); }
+
 protected:
     virtual void notifyFinished(CachedResource*);
 
@@ -86,12 +98,14 @@ private:
     void updateRenderer();
 
     void setImageWithoutConsideringPendingLoadEvent(CachedImage*);
+    void sourceImageChanged();
     void clearFailedLoadURL();
 
     void timerFired(Timer<ImageLoader>*);
 
     Element* m_element;
     CachedResourceHandle<CachedImage> m_image;
+    HashSet<ImageLoaderClient*> m_clients;
     Timer<ImageLoader> m_derefElementTimer;
     AtomicString m_failedLoadURL;
     bool m_hasPendingBeforeLoadEvent : 1;