Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/loader/ImageLoader.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef ImageLoader_h
 #define ImageLoader_h
 
 #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;
 
 template<typename T> class EventSender;
 typedef EventSender<ImageLoader> ImageEventSender;
 
 class ImageLoader : public CachedImageClient {
 public:
     explicit ImageLoader(Element*);
@@ skipping 19 matching lines @@
 
     bool hasPendingBeforeLoadEvent() const { return m_hasPendingBeforeLoadEvent; }
     bool hasPendingActivity() const { return m_hasPendingLoadEvent || m_hasPendingErrorEvent; }
 
     void dispatchPendingEvent(ImageEventSender*);
 
     static void dispatchPendingBeforeLoadEvents();
     static void dispatchPendingLoadEvents();
     static void dispatchPendingErrorEvents();
 
+    void addClient(ImageLoaderClient* client) { m_clients.add(client); }

[Stephen White, 2013/07/25 18:01:07]

I'm not sure if the ImageLoader is really the right place for this, since it's
not really related to image loading per se. IIUC, you want to watch changes to
the Image element's src attribute. I'm wondering if there's an observer or
something at the DOM level that you could use for this.

+    void removeClient(ImageLoaderClient* client) { m_clients.remove(client); }
+
 protected:
     virtual void notifyFinished(CachedResource*);
 
 private:
     virtual void dispatchLoadEvent() = 0;
     virtual String sourceURI(const AtomicString&) const = 0;
 
     void updatedHasPendingEvent();
 
     void dispatchPendingBeforeLoadEvent();
     void dispatchPendingLoadEvent();
     void dispatchPendingErrorEvent();
 
     RenderImageResource* renderImageResource();
     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;
     bool m_hasPendingLoadEvent : 1;
     bool m_hasPendingErrorEvent : 1;
     bool m_imageComplete : 1;
     bool m_loadManually : 1;
     bool m_elementIsProtected : 1;
 };
 
 }
 
 #endif