Disable display item caching

Source/platform/graphics/paint/DisplayItemList.h

Index: Source/platform/graphics/paint/DisplayItemList.h
diff --git a/Source/platform/graphics/paint/DisplayItemList.h b/Source/platform/graphics/paint/DisplayItemList.h
index af2af340d891d8a2dffb59b881ec9391b2e50b0c..72c610d1998f127082e2a7f938baef8f362ae176 100644
--- a/Source/platform/graphics/paint/DisplayItemList.h
+++ b/Source/platform/graphics/paint/DisplayItemList.h
@@ -23,12 +23,15 @@ class PLATFORM_EXPORT DisplayItemList {
 public:
     static PassOwnPtr<DisplayItemList> create() { return adoptPtr(new DisplayItemList); }
 
+    void beginNewPaints();
+    void endNewPaints();
+
     const PaintList& paintList();
     void add(WTF::PassOwnPtr<DisplayItem>);
 
     void invalidate(DisplayItemClient);
     void invalidateAll();
-    bool clientCacheIsValid(DisplayItemClient client) const { return m_cachedClients.contains(client); }
+    bool clientCacheIsValid(DisplayItemClient) const;
 
     // Plays back the current PaintList() into the given context.
     void replay(GraphicsContext*);
@@ -38,7 +41,7 @@ public:
 #endif
 
 protected:
-    DisplayItemList() { };
+    DisplayItemList() : m_doingNewPaints(false) { };
 
 private:
     PaintList::iterator findNextMatchingCachedItem(PaintList::iterator, const DisplayItem&);
@@ -51,6 +54,7 @@ private:
 
     PaintList m_paintList;
     HashSet<DisplayItemClient> m_cachedClients;
+    bool m_doingNewPaints;
     PaintList m_newPaints;
 };