Allow eviction of ImageBitmaps that are created from ImageElements.

Source/core/loader/cache/CachedResource.cpp

Index: Source/core/loader/cache/CachedResource.cpp
diff --git a/Source/core/loader/cache/CachedResource.cpp b/Source/core/loader/cache/CachedResource.cpp
index 80c261fc9ebd15b0b6f2c83efa8b7c9154954cbe..55261d97cf18d62491e20871350210bea8a086ac 100644
--- a/Source/core/loader/cache/CachedResource.cpp
+++ b/Source/core/loader/cache/CachedResource.cpp
@@ -106,6 +106,7 @@ CachedResource::CachedResource(const ResourceRequest& request, Type type)
     , m_handleCount(0)
     , m_preloadCount(0)
     , m_preloadResult(PreloadNotReferenced)
+    , m_cachePriority(CachePriorityLow)
     , m_inLiveDecodedResourcesList(false)
     , m_requestedFromNetworkingLayer(false)
     , m_inCache(false)
@@ -343,6 +344,19 @@ CachedMetadata* CachedResource::cachedMetadata(unsigned dataTypeID) const
     return m_cachedMetadata.get();
 }
 
+void CachedResource::setCachePriority(CachePriority priority)
+{
+    m_lastDecodedAccessTime = currentTime();
+    if (inCache()) {
+        if (m_inLiveDecodedResourcesList && m_cachePriority != priority) {
+            memoryCache()->removeFromLiveDecodedResourcesList(this);
+            m_cachePriority = priority;
+            memoryCache()->insertInLiveDecodedResourcesList(this);
+        }
+        memoryCache()->prune();
+    }
+}
+
 void CachedResource::clearLoader()
 {
     m_loader = 0;
@@ -825,3 +839,4 @@ void CachedResource::CachedResourceCallback::timerFired(Timer<CachedResourceCall
 }
 
 }
+