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

Source/wtf/MainThread.h

 /*
  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
  *
  * 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.
@@ skipping 12 matching lines @@
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef MainThread_h
 #define MainThread_h
 
+#include "wtf/Forward.h"
+#include "wtf/WTFExport.h"
 #include <stdint.h>
 
-#include "wtf/WTFExport.h"
-
 namespace WTF {
 
 typedef void MainThreadFunction(void*);
 
 // Must be called from the main thread.
 WTF_EXPORT void initializeMainThread(void (*)(MainThreadFunction, void*));
 
 WTF_EXPORT void callOnMainThread(MainThreadFunction*, void* context);
 
-template<typename> class Function;
-WTF_EXPORT void callOnMainThread(const Function<void ()>&);
+WTF_EXPORT void callOnMainThread(PassOwnPtr<Function<void()>>);
 
 WTF_EXPORT bool isMainThread();
 
 } // namespace WTF
 
 using WTF::callOnMainThread;
 using WTF::isMainThread;
 #endif // MainThread_h