Add thread affinity and ASSERT() for same-thread restriction to WTF::Function

third_party/WebKit/Source/platform/threading/BackgroundTaskRunner.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BackgroundTaskRunner_h
 #define BackgroundTaskRunner_h
 
 #include "platform/PlatformExport.h"
 #include "wtf/Functional.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class WebTraceLocation;
 
 namespace BackgroundTaskRunner {
 
 enum TaskSize {
     TaskSizeShortRunningTask,
     TaskSizeLongRunningTask,
 };
 
-PLATFORM_EXPORT void postOnBackgroundThread(const WebTraceLocation&, PassOwnPtr<Closure>, TaskSize);
+PLATFORM_EXPORT void postOnBackgroundThread(const WebTraceLocation&, PassOwnPtr<CrossThreadClosure>, TaskSize);
 
 } // BackgroundTaskRunner
 
 } // namespace blink
 
 #endif