C++ readability review

components/timers/alarm_timer.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 COMPONENTS_TIMER_ALARM_TIMER_H_
-#define COMPONENTS_TIMER_ALARM_TIMER_H_
-
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/weak_ptr.h"
-#include "base/message_loop/message_loop.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-
-namespace base {
-struct PendingTask;
-}
-
-namespace timers {
-// The class implements a timer that is capable of waking the system up from a
-// suspended state.  For example, this is useful for running tasks that are
-// needed for maintaining network connectivity, like sending heartbeat messages.
-// Currently, this feature is only available on Chrome OS systems running linux
-// version 3.11 or higher.  On all other platforms, the AlarmTimer behaves
-// exactly the same way as a regular Timer.
-class AlarmTimer : public base::Timer,
-                   public base::MessageLoop::DestructionObserver {
- public:
-  // The delegate is responsible for managing the system level details for
-  // actually setting up and monitoring a timer that is capable of waking the
-  // system from suspend.  This class is reference counted because it may need
-  // to outlive the timer in order to clean up after itself.
-  class Delegate : public base::RefCountedThreadSafe<Delegate> {
-   public:
-    // Initializes the timer.  Should return true iff the system has timers that
-    // can wake it up from suspend.  Will only be called once.
-    virtual bool Init(base::WeakPtr<AlarmTimer> timer) = 0;
-
-    // Stops the currently running timer.  It should be safe to call this more
-    // than once.
-    virtual void Stop() = 0;
-
-    // Resets the timer to fire after |delay| has passed.  Cancels any
-    // pre-existing delay.
-    virtual void Reset(base::TimeDelta delay) = 0;
-
-   protected:
-    virtual ~Delegate() {}
-
-   private:
-    friend class base::RefCountedThreadSafe<Delegate>;
-  };
-
-  AlarmTimer(bool retain_user_task, bool is_repeating);
-
-  AlarmTimer(const tracked_objects::Location& posted_from,
-             base::TimeDelta delay,
-             const base::Closure& user_task,
-             bool is_repeating);
-
-  ~AlarmTimer() override;
-
-  bool can_wake_from_suspend() const { return can_wake_from_suspend_; }
-
-  // Must be called by the delegate to indicate that the timer has fired and
-  // that the user task should be run.
-  void OnTimerFired();
-
-  // Timer overrides.
-  void Stop() override;
-  void Reset() override;
-
-  // MessageLoop::DestructionObserver overrides.
-  void WillDestroyCurrentMessageLoop() override;
-
- private:
-  // Initializes the timer with the appropriate delegate.
-  void Init();
-
-  // Delegate that will manage actually setting the timer.
-  scoped_refptr<Delegate> delegate_;
-
-  // Keeps track of the user task we want to run.  A new one is constructed
-  // every time Reset() is called.
-  scoped_ptr<base::PendingTask> pending_task_;
-
-  // Tracks whether the timer has the ability to wake the system up from
-  // suspend.  This is a runtime check because we won't know if the system
-  // supports being woken up from suspend until the delegate actually tries to
-  // set it up.
-  bool can_wake_from_suspend_;
-
-  // Pointer to the message loop that started the timer.  Used to track the
-  // destruction of that message loop.
-  base::MessageLoop* origin_message_loop_;
-
-  base::WeakPtrFactory<AlarmTimer> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(AlarmTimer);
-};
-
-}  // namespace timers
-
-#endif  // COMPONENTS_TIMER_ALARM_TIMER_H_