Replace forward declarations with includes in TaskRunner APIs.

base/task_runner.h

 // Copyright (c) 2012 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 BASE_TASK_RUNNER_H_
 #define BASE_TASK_RUNNER_H_
 
 #include <stddef.h>
 
 #include "base/base_export.h"
 #include "base/callback_forward.h"
+#include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 
-namespace tracked_objects {
-class Location;
-} // namespace tracked_objects
-
 namespace base {
 
 struct TaskRunnerTraits;
 
 // A TaskRunner is an object that runs posted tasks (in the form of
 // Closure objects).  The TaskRunner interface provides a way of
 // decoupling task posting from the mechanics of how each task will be
 // run.  TaskRunner provides very weak guarantees as to how posted
 // tasks are run (or if they're run at all).  In particular, it only
 // guarantees:
@@ skipping 116 matching lines @@
   virtual void OnDestruct() const;
 };
 
 struct BASE_EXPORT TaskRunnerTraits {
   static void Destruct(const TaskRunner* task_runner);
 };
 
 }  // namespace base
 
 #endif  // BASE_TASK_RUNNER_H_