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

chrome/browser/after_startup_task_utils.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 CHROME_BROWSER_AFTER_STARTUP_TASK_UTILS_H_
 #define CHROME_BROWSER_AFTER_STARTUP_TASK_UTILS_H_
 
 #include "base/bind.h"
+#include "base/callback.h"

[sky, 2017/03/22 17:34:11]

callback_forward?

[gab, 2017/03/22 17:46:45]

Need full type to pass by value.

 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/task_runner.h"
 
 namespace android {
 class AfterStartupTaskUtilsJNI;
 }
 
 class AfterStartupTaskUtils {
  public:
   // A helper TaskRunner which merely forwards to
   // AfterStartupTaskUtils::PostTask(). Doesn't support tasks with a non-zero
   // delay.
   class Runner : public base::TaskRunner {
    public:
     explicit Runner(scoped_refptr<base::TaskRunner> destination_runner);
 
     // Overrides from base::TaskRunner:
     bool PostDelayedTask(const tracked_objects::Location& from_here,
-                         const base::Closure& task,
+                         base::Closure task,
                          base::TimeDelta delay) override;
     bool RunsTasksOnCurrentThread() const override;
 
    private:
     ~Runner() override;
 
     const scoped_refptr<base::TaskRunner> destination_runner_;
 
     DISALLOW_COPY_AND_ASSIGN(Runner);
   };
 
   // Observes startup and when complete runs tasks that have accrued.
   static void StartMonitoringStartup();
 
   // Used to augment the behavior of BrowserThread::PostAfterStartupTask
   // for chrome. Tasks are queued until startup is complete.
   // Note: see browser_thread.h
   static void PostTask(
       const tracked_objects::Location& from_here,
       const scoped_refptr<base::TaskRunner>& destination_runner,
-      const base::Closure& task);
+      base::Closure task);
 
   // Returns true if browser startup is complete. Only use this on a one-off
   // basis; If you need to poll this function constantly, use the above
   // PostTask() API instead.
   static bool IsBrowserStartupComplete();
 
   // For use by unit tests where we don't have normal content loading
   // infrastructure and thus StartMonitoringStartup() is unsuitable.
   static void SetBrowserStartupIsCompleteForTesting();
 
   static void UnsafeResetForTesting();
 
  private:
   // TODO(wkorman): Look into why Android calls
   // SetBrowserStartupIsComplete() directly. Ideally it would use
   // StartMonitoringStartup() as the normal approach.
   friend class android::AfterStartupTaskUtilsJNI;
 
   static void SetBrowserStartupIsComplete();
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AfterStartupTaskUtils);
 };
 
 #endif  // CHROME_BROWSER_AFTER_STARTUP_TASK_UTILS_H_