Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/loader/cache/CachedResource.h

Index: Source/core/loader/cache/CachedResource.h
diff --git a/Source/core/loader/cache/CachedResource.h b/Source/core/loader/cache/CachedResource.h
index b9c6f778fcd40d7247d28aa2c579a2d346087cf5..7d1dba5fc3b77e0b281ab6b4aa5c35fb21c9637e 100644
--- a/Source/core/loader/cache/CachedResource.h
+++ b/Source/core/loader/cache/CachedResource.h
@@ -80,6 +80,13 @@ public:
         DecodeError
     };
 
+    // Determines the order in which CachedResources are evicted
+    // from the decoded resources cache.
+    enum CacheLiveResourcePriority {
+        CacheLiveResourcePriorityLow = 0,
+        CacheLiveResourcePriorityHigh
+    };
+
     CachedResource(const ResourceRequest&, Type);
     virtual ~CachedResource();
 
@@ -167,6 +174,8 @@ public:
     void setInCache(bool inCache) { m_inCache = inCache; }
     bool inCache() const { return m_inCache; }
     
+    void setCacheLiveResourcePriority(CacheLiveResourcePriority);
+    unsigned cacheLiveResourcePriority() const { return m_cacheLiveResourcePriority; }
     bool inLiveDecodedResourcesList() { return m_inLiveDecodedResourcesList; }
     
     void clearLoader();
@@ -310,6 +319,7 @@ private:
     unsigned m_preloadCount;
 
     unsigned m_preloadResult : 2; // PreloadResult
+    unsigned m_cacheLiveResourcePriority : 2; // CacheLiveResourcePriority
 
     bool m_inLiveDecodedResourcesList : 1;
     bool m_requestedFromNetworkingLayer : 1;