High resolution timer fix reland

base/message_loop/message_loop.h

 // Copyright 2013 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_MESSAGE_LOOP_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 
 #include <queue>
 #include <string>
 
@@ skipping 353 matching lines @@
 
    protected:
     virtual ~TaskObserver();
   };
 
   // These functions can only be called on the same thread that |this| is
   // running on.
   void AddTaskObserver(TaskObserver* task_observer);
   void RemoveTaskObserver(TaskObserver* task_observer);
 
-  // When we go into high resolution timer mode, we will stay in hi-res mode
-  // for at least 1s.
-  static const int kHighResolutionTimerModeLeaseTimeMs = 1000;
-
 #if defined(OS_WIN)
   void set_os_modal_loop(bool os_modal_loop) {
     os_modal_loop_ = os_modal_loop;
   }
 
   bool os_modal_loop() const {
     return os_modal_loop_;
   }
 #endif  // OS_WIN
 
   // Can only be called from the thread that owns the MessageLoop.
   bool is_running() const;
 
   // Returns true if the message loop has high resolution timers enabled.
   // Provided for testing.
-  bool IsHighResolutionTimerEnabledForTesting();
+  bool HasHighResolutionTasks();
 
   // Returns true if the message loop is "idle". Provided for testing.
   bool IsIdleForTesting();
 
   //----------------------------------------------------------------------------
  protected:
   scoped_ptr<MessagePump> pump_;
 
  private:
   friend class internal::IncomingTaskQueue;
@@ skipping 48 matching lines @@
   virtual bool DoWork() OVERRIDE;
   virtual bool DoDelayedWork(TimeTicks* next_delayed_work_time) OVERRIDE;
   virtual bool DoIdleWork() OVERRIDE;
 
   const Type type_;
 
   // A list of tasks that need to be processed by this instance.  Note that
   // this queue is only accessed (push/pop) by our current thread.
   TaskQueue work_queue_;
 
+  // How many high resolution tasks are in the pending task queue. This value
+  // increases by N every time we call ReloadWorkQueue() and decreases by 1
+  // every time we call RunTask() if the task needs a high resolution timer.
+  int pending_high_res_tasks_;
+  // Tracks if we have requested high resolution timers. Its only use is to
+  // turn off the high resolution timer upon loop destruction.
+  bool in_high_res_mode_;
+
   // Contains delayed tasks, sorted by their 'delayed_run_time' property.
   DelayedTaskQueue delayed_work_queue_;
 
   // A recent snapshot of Time::Now(), used to check delayed_work_queue_.
   TimeTicks recent_time_;
 
   // A queue of non-nestable tasks that we had to defer because when it came
   // time to execute them we were in a nested message loop.  They will execute
   // once we're out of nested message loops.
   TaskQueue deferred_non_nestable_work_queue_;
@@ skipping 174 matching lines @@
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_