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

Source/core/fetch/DocumentResourceReference.h

Index: Source/core/fetch/DocumentResourceReference.h
diff --git a/Source/core/fetch/DocumentResourceReference.h b/Source/core/fetch/DocumentResourceReference.h
index 46f9bf5167a4579d30d88c50c3521426ec7df47a..c5936bdbbc404dc5564d5d76b17d1bb9fcdb078d 100644
--- a/Source/core/fetch/DocumentResourceReference.h
+++ b/Source/core/fetch/DocumentResourceReference.h
@@ -32,6 +32,7 @@
 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); }