Clean up remaining uses of WebCore namespace

Source/platform/heap/Handle.h

Index: Source/platform/heap/Handle.h
diff --git a/Source/platform/heap/Handle.h b/Source/platform/heap/Handle.h
index 7d7195df7d164566b5c9e0d0a3629bd2d4f0985d..7cf6b5d6dab6eaa2f39f627490d6087ac4c192d8 100644
--- a/Source/platform/heap/Handle.h
+++ b/Source/platform/heap/Handle.h
@@ -697,7 +697,7 @@ template <typename T> struct RemoveHeapPointerWrapperTypes {
 };
 
 template<typename T>
-struct TraceIfNeeded : public TraceIfEnabled<T, WebCore::IsGarbageCollectedType<typename RemoveHeapPointerWrapperTypes<typename WTF::RemovePointer<T>::Type>::Type>::value> { };
+struct TraceIfNeeded : public TraceIfEnabled<T, blink::IsGarbageCollectedType<typename RemoveHeapPointerWrapperTypes<typename WTF::RemovePointer<T>::Type>::Type>::value> { };
 
 // This trace trait for std::pair will null weak members if their referent is
 // collected. If you have a collection that contain weakness it does not remove