New display item caching

Source/platform/graphics/paint/DisplayItem.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DisplayItem_h
 #define DisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "wtf/Assertions.h"
 #include "wtf/PassOwnPtr.h"
@@ skipping 101 matching lines @@
     static WTF::String typeAsDebugString(DisplayItem::Type);
 
     void setClientDebugString(const WTF::String& clientDebugString) { m_clientDebugString = clientDebugString; }
     const WTF::String& clientDebugString() const { return m_clientDebugString; }
 
     WTF::String asDebugString() const;
     virtual const char* name() const { return "Dummy"; }
     virtual void dumpPropertiesAsDebugString(WTF::StringBuilder&) const;
 #endif
 
+    // FIXME: Replace these virtual functions with static field access.
     virtual bool isCached() const { return false; }
+    virtual bool isSubtreeCached() const { return false; }
+    virtual bool isBeginSubtree() const { return false; }
+    virtual bool isEndSubtree() const { return false; }
 
 protected:
     DisplayItem(DisplayItemClient client, Type type)
         : m_id(client, type)
     {
         ASSERT(client);
     }
 
 private:
     struct Id {
         Id(DisplayItemClient c, Type t)
             : client(c)
             , type(t)
         {
             ASSERT(client);
         }
 
         const DisplayItemClient client;
         const Type type;
     } m_id;
 #ifndef NDEBUG
     WTF::String m_clientDebugString;
 #endif
 };
 
 }
 
 #endif // DisplayItem_h