Oilpan: move WorkerGlobalScope to oilpan's heap.

Source/heap/Heap.h

Index: Source/heap/Heap.h
diff --git a/Source/heap/Heap.h b/Source/heap/Heap.h
index 920658953acf6c19397685f90e5c2e51163bd33b..a936fbabd9a86b867d7e65b4beab231f283437c2 100644
--- a/Source/heap/Heap.h
+++ b/Source/heap/Heap.h
@@ -1361,6 +1361,13 @@ struct ThreadingTrait<HashMap<Key, Value, HeapAllocator, T, U, V> > {
         && (ThreadingTrait<Value>::Affinity == MainThreadOnly) ? MainThreadOnly : AnyThread;
 };
 
+template<typename First, typename Second>
+struct ThreadingTrait<WTF::KeyValuePair<First, Second> > {
+    static const ThreadAffinity Affinity =
+        (ThreadingTrait<First>::Affinity == MainThreadOnly)
+        && (ThreadingTrait<Second>::Affinity == MainThreadOnly) ? MainThreadOnly : AnyThread;
+};
+
 template<typename T, typename U, typename V>
 struct ThreadingTrait<HashSet<T, HeapAllocator, U, V> > {
     static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;