Replace RenderArena with PartitionAlloc

Source/core/platform/Partitions.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 23 matching lines @@
 #include "wtf/PartitionAlloc.h"
 
 namespace WebCore {
 
 class Partitions {
 public:
     static void init();
     static void shutdown();
 
     ALWAYS_INLINE static PartitionRoot* getObjectModelPartition() { return &m_objectModelRoot; }
+    ALWAYS_INLINE static PartitionRoot* getRenderingPartition() { return &m_renderingRoot; }
 
 private:
     static PartitionRoot m_objectModelRoot;
+    static PartitionRoot m_renderingRoot;
 };
 
 } // namespace WebCore
 
 #endif // Partitions_h