Pass Callback to TaskRunner by value and consume it on invocation (1)

ios/web/web_thread_impl.h

 // Copyright 2014 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 IOS_WEB_WEB_THREAD_IMPL_H_
 #define IOS_WEB_WEB_THREAD_IMPL_H_
 
+#include "base/callback.h"
 #include "base/threading/thread.h"
 #include "ios/web/public/web_thread.h"
 
 namespace web {
 
 class WebTestSuiteListener;
 
 class WebThreadImpl : public WebThread, public base::Thread {
  public:
   // Construct a WebThreadImpl with the supplied identifier.  It is an error
@@ skipping 23 matching lines @@
   // the thread id from the callstack alone in crash dumps.
   void UIThreadRun(base::RunLoop* run_loop);
   void DBThreadRun(base::RunLoop* run_loop);
   void FileThreadRun(base::RunLoop* run_loop);
   void FileUserBlockingThreadRun(base::RunLoop* run_loop);
   void CacheThreadRun(base::RunLoop* run_loop);
   void IOThreadRun(base::RunLoop* run_loop);
 
   static bool PostTaskHelper(WebThread::ID identifier,
                              const tracked_objects::Location& from_here,
-                             const base::Closure& task,
+                             base::Closure task,
                              base::TimeDelta delay,
                              bool nestable);
 
   // Common initialization code for the constructors.
   void Initialize();
 
   // Performs cleanup that needs to happen on the IO thread before calling the
   // embedder's CleanUp function.
   void IOThreadPreCleanUp();
 
   // For testing.
   friend class TestWebThreadBundle;
   friend class TestWebThreadBundleImpl;
   friend class WebTestSuiteListener;
   static void FlushThreadPoolHelperForTesting();
 
   // The identifier of this thread.  Only one thread can exist with a given
   // identifier at a given time.
   ID identifier_;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_WEB_THREAD_IMPL_H_