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

Source/core/dom/Microtask.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 55 matching lines @@
     OwnPtr<WebThread::Task> task = adoptPtr(static_cast<WebThread::Task*>(data));
     task->run();
 }
 
 void Microtask::enqueueMicrotask(PassOwnPtr<WebThread::Task> callback)
 {
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
     isolate->EnqueueMicrotask(&microtaskFunctionCallback, callback.leakPtr());
 }
 
-void Microtask::enqueueMicrotask(const Closure& callback)
+void Microtask::enqueueMicrotask(PassOwnPtr<Closure> callback)
 {
     enqueueMicrotask(adoptPtr(new Task(callback)));
 }
 
 } // namespace blink