Make classes and structures in core/events and core/fetch fast-allocated.

Source/core/fetch/DocumentResourceReference.h

 /*
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 14 matching lines @@
 
 #ifndef DocumentResourceReference_h
 #define DocumentResourceReference_h
 
 #include "core/fetch/DocumentResource.h"
 #include "core/fetch/ResourcePtr.h"
 
 namespace blink {
 
 class DocumentResourceReference final : public DocumentResourceClient {
+    WTF_MAKE_FAST_ALLOCATED(DocumentResourceReference);

[haraken, 2015/08/24 10:59:12]

Our plan is to add the macro only to the most parent class, isn't it?

[tasak, 2015/08/25 03:54:41]

I think, "if possible, we will add the macro to the most parent class."
We should consider multiple inheritance. 
FYI:
class SVGUseElement final : public SVGGraphicsElement,
                            public SVGURIReference,
                            public DocumentResourceClient

SVGUseElement=> SVGraphicsElement => SVGElement => Element => ContainerNode =>
Node (Node has operator new)

If we see  WILL_BE_USING_GARBAGE_COLLECTED_MIXIN",  we should be careful.

 public:
     DocumentResourceReference(DocumentResource* document) : m_document(document) { m_document->addClient(this); }
     ~DocumentResourceReference() override { m_document->removeClient(this); }
     DocumentResource* document() { return m_document.get(); }
 private:
     ResourcePtr<DocumentResource> m_document;
 };
 
 };
 
 #endif