Oilpan: Replace RefPtrs to Node and its subclasses in core/dom/ with Oilpan transtion types.

Source/platform/heap/Handle.h

 /*
  * Copyright (C) 2014 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 534 matching lines @@
     {
         return static_cast<U*>(m_raw);
     }
 
     bool operator!() const { return !m_raw; }
 
     operator T*() const { return m_raw; }
 
     T* operator->() const { return m_raw; }
     T& operator*() const { return *m_raw; }
-    operator RawPtr<T>() const { return m_raw; }
+    template<typename U>
+    operator RawPtr<U>() const { return m_raw; }

[zerny-chromium, 2014/06/04 09:28:18]

Generalizing this operator causes ambiguity since we can then convert a
Member/Persistent to a RawPtr<U> or a U*. Is it strictly needed for this change?
I found that too many protect(foo)'s had to have an added .get() for this to
work...

[tkent, 2014/06/05 00:22:27]

Without this, we need to add dozens of .get() to code like the following:

    RefPtrWillBeMember<HTMLFooElement> m_foo;
    ....
    parent->appendChild(m_foo);

With this, we need to add just one .get() for HTMLLinkElement.cpp in this CL.
Almost all instances of protect(foo) is not for Member<>.

 
     template<typename U>
     Member& operator=(const Persistent<U>& other)
     {
         m_raw = other;
         return *this;
     }
 
     template<typename U>
     Member& operator=(const Member<U>& other)
@@ skipping 581 matching lines @@
 struct NeedsTracing<ListHashSetNode<T, WebCore::HeapListHashSetAllocator<T, inlineCapacity> > *> {
     // All heap allocated node pointers need visiting to keep the nodes alive,
     // regardless of whether they contain pointers to other heap allocated
     // objects.
     static const bool value = true;
 };
 
 } // namespace WTF
 
 #endif