Add synonyms for collection types over MutationObserver-related types.

Source/core/dom/MutationObserver.h

Index: Source/core/dom/MutationObserver.h
diff --git a/Source/core/dom/MutationObserver.h b/Source/core/dom/MutationObserver.h
index 3d92d18bffd293a1c8c500d7a9f287c51fb31275..03d1d9ece153502e416cb4dacd05f80cec8ad4b3 100644
--- a/Source/core/dom/MutationObserver.h
+++ b/Source/core/dom/MutationObserver.h
@@ -45,6 +45,7 @@ namespace WebCore {
 class Dictionary;
 class ExceptionState;
 class MutationCallback;
+class MutationObserver;
 class MutationObserverRegistration;
 class MutationRecord;
 class Node;
@@ -52,6 +53,11 @@ class Node;
 typedef unsigned char MutationObserverOptions;
 typedef unsigned char MutationRecordDeliveryOptions;
 
+typedef WillBeHeapHashSet<RefPtrWillBeMember<MutationObserver> > MutationObserverSet;
+typedef WillBeHeapHashSet<RawPtrWillBeMember<MutationObserverRegistration> > MutationObserverRegistrationSet;
+typedef WillBeHeapVector<RefPtrWillBeMember<MutationObserver> > MutationObserverVector;
+typedef WillBeHeapVector<RefPtrWillBeMember<MutationRecord> > MutationRecordVector;
+
 class MutationObserver FINAL : public RefCountedWillBeGarbageCollectedFinalized<MutationObserver>, public ScriptWrappable {
 public:
     enum MutationType {
@@ -98,8 +104,8 @@ private:
     void deliver();
 
     OwnPtr<MutationCallback> m_callback;
-    WillBeHeapVector<RefPtrWillBeMember<MutationRecord> > m_records;
-    WillBeHeapHashSet<RawPtrWillBeMember<MutationObserverRegistration> > m_registrations;
+    MutationRecordVector m_records;
+    MutationObserverRegistrationSet m_registrations;
     unsigned m_priority;
 };