Oilpan: move DOM string collection objects to the Oilpan heap.

Source/core/dom/DOMStringMap.h

Index: Source/core/dom/DOMStringMap.h
diff --git a/Source/core/dom/DOMStringMap.h b/Source/core/dom/DOMStringMap.h
index fb4d17bc72d67e05e552096d2f58cd18be92ec2a..83095794734d6d4bad7e8974a35c44d116f4c2bf 100644
--- a/Source/core/dom/DOMStringMap.h
+++ b/Source/core/dom/DOMStringMap.h
@@ -29,6 +29,7 @@
 #include "bindings/v8/ExceptionState.h"
 #include "bindings/v8/ScriptWrappable.h"
 #include "bindings/v8/V8Binding.h"
+#include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
@@ -37,13 +38,16 @@ namespace WebCore {
 
 class Element;
 
-class DOMStringMap : public ScriptWrappable {
-    WTF_MAKE_NONCOPYABLE(DOMStringMap); WTF_MAKE_FAST_ALLOCATED;
+class DOMStringMap : public NoBaseWillBeGarbageCollectedFinalized<DOMStringMap>, public ScriptWrappable {
+    WTF_MAKE_NONCOPYABLE(DOMStringMap);
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     virtual ~DOMStringMap();
 
+#if !ENABLE(OILPAN)
     virtual void ref() = 0;
     virtual void deref() = 0;
+#endif
 
     virtual void getNames(Vector<String>&) = 0;
     virtual String item(const String& name) = 0;
@@ -81,6 +85,8 @@ public:
 
     virtual Element* element() = 0;
 
+    virtual void trace(Visitor*) { }
+
 protected:
     DOMStringMap()
     {