Subtree caching implementation in blink-core

Source/platform/graphics/paint/SubtreeRecorder.h

 // Copyright 2015 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 SubtreeRecorder_h
 #define SubtreeRecorder_h
 
 #include "platform/graphics/paint/DisplayItemClient.h"
 
 namespace blink {
 
 class DisplayItemList;
 class GraphicsContext;
 
 // Records subtree information during painting. The recorder's life span covers
 // all painting operations executed during the root of the subtree's paint method
 // for the paint phase.
 class PLATFORM_EXPORT SubtreeRecorder {
 public:
+    static bool useCachedSubtreeIfPossible(GraphicsContext&, const DisplayItemClientWrapper&, int paintPhase);
+
     SubtreeRecorder(GraphicsContext&, const DisplayItemClientWrapper&, int paintPhase);
     ~SubtreeRecorder();
 
-    bool canUseCache() const;
-
 private:
     DisplayItemList* m_displayItemList;
     DisplayItemClientWrapper m_client;
     const int m_paintPhase;
-    bool m_canUseCache;
-#if ENABLE(ASSERT)
-    mutable bool m_checkedCanUseCache;
-#endif
 };
 
 } // namespace blink
 
 #endif // SubtreeRecorder_h