Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/loader/cache/CachedResource.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.
@@ skipping 62 matching lines @@
     };
 
     enum Status {
         Unknown,      // let cache decide what to do with it
         Pending,      // only partially loaded
         Cached,       // regular case
         LoadError,
         DecodeError
     };
 
+    enum DecodePriority {

[Justin Novosad, 2013/07/23 16:55:12]

Hmmm... this name sounds like it determines which image will be decoded before
the others, which is not what it is for. How about calling it CachePriority?

+        DecodePriorityLow = 0,
+        DecodePriorityMedium,
+        DecodePriorityHigh
+    };
+
     CachedResource(const ResourceRequest&, Type);
     virtual ~CachedResource();
 
     virtual void load(CachedResourceLoader*, const ResourceLoaderOptions&);
 
     virtual void setEncoding(const String&) { }
     virtual String encoding() const { return String(); }
     virtual void appendData(const char*, int);
     virtual void error(CachedResource::Status);
 
@@ skipping 69 matching lines @@
     bool passesAccessControlCheck(SecurityOrigin*, String& errorDescription);
     bool canBeAccessedBy(SecurityOrigin*, String& error);
 
     // Called by the cache if the object has been removed from the cache
     // while still being referenced. This means the object should delete itself
     // if the number of clients observing it ever drops to 0.
     // The resource can be brought back to cache after successful revalidation.
     void setInCache(bool inCache) { m_inCache = inCache; }
     bool inCache() const { return m_inCache; }
     
+    void setDecodePriority(DecodePriority);
+    DecodePriority decodePriority() const { return m_decodePriority; }
     bool inLiveDecodedResourcesList() { return m_inLiveDecodedResourcesList; }
     
     void clearLoader();
 
     SharedBuffer* resourceBuffer() const { ASSERT(!m_purgeableData); return m_data.get(); }
 
     virtual void willSendRequest(ResourceRequest&, const ResourceResponse&) { m_requestedFromNetworkingLayer = true; }
     virtual void responseReceived(const ResourceResponse&);
     void setResponse(const ResourceResponse& response) { m_response = response; }
     const ResourceResponse& response() const { return m_response; }
@@ skipping 128 matching lines @@
     unsigned long m_identifier;
 
     unsigned m_encodedSize;
     unsigned m_decodedSize;
     unsigned m_accessCount;
     unsigned m_handleCount;
     unsigned m_preloadCount;
 
     unsigned m_preloadResult : 2; // PreloadResult
 
+    DecodePriority m_decodePriority;
     bool m_inLiveDecodedResourcesList : 1;
     bool m_requestedFromNetworkingLayer : 1;
 
     bool m_inCache : 1;
     bool m_loading : 1;
 
     bool m_switchingClientsToRevalidatedResource : 1;
 
     unsigned m_type : 4; // Type
     unsigned m_status : 3; // Status
@@ skipping 18 matching lines @@
     // If this field is non-null, the resource has a proxy for checking whether it is still up to date (see m_resourceToRevalidate).
     CachedResource* m_proxyResource;
 
     // These handles will need to be updated to point to the m_resourceToRevalidate in case we get 304 response.
     HashSet<CachedResourceHandleBase*> m_handlesToRevalidate;
 };
 
 }
 
 #endif