Change the return type of WTF::bind() to |OwnPtr<Function>|

Source/core/dom/Microtask.h

Index: Source/core/dom/Microtask.h
diff --git a/Source/core/dom/Microtask.h b/Source/core/dom/Microtask.h
index 03a5b3225739f57b566021a4237913402bf7ba7c..5ee4f533d22b51d2a9a28e75b9aea0a33c612c30 100644
--- a/Source/core/dom/Microtask.h
+++ b/Source/core/dom/Microtask.h
@@ -43,7 +43,7 @@ public:
     static void performCheckpoint();
     static bool performingCheckpoint(v8::Isolate*);
     static void enqueueMicrotask(PassOwnPtr<WebThread::Task>);
-    static void enqueueMicrotask(const Closure&);
+    static void enqueueMicrotask(PassOwnPtr<Closure>);
 
 private:
     explicit Microtask();