Revert of Gardening: Revert "Use AudioStreamMonitor to control power save blocking."

chrome/browser/media/audio_stream_monitor.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 CHROME_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
-#define CHROME_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
-
-#include <map>
-
-#include "base/callback_forward.h"
-#include "base/threading/thread_checker.h"
-#include "base/time/default_tick_clock.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-#include "content/public/browser/web_contents_user_data.h"
-
-namespace base {
-class TickClock;
-}
-
-// Repeatedly polls audio streams for their power levels, and "debounces" the
-// information into a simple, binary "was recently audible" result for the audio
-// indicators in the tab UI.  The debouncing logic is to: 1) Turn on immediately
-// when sound is audible; and 2) Hold on for X amount of time after sound has
-// gone silent, then turn off.  Said another way, we don't want tab indicators
-// to turn on/off repeatedly and annoy the user.  AudioStreamMonitor sends UI
-// update notifications only when needed, but may be queried at any time.
-//
-// There are zero or one instances of AudioStreamMonitor per
-// content::WebContents instance (referred to as "the tab" in comments below).
-// AudioStreamMonitor is created on-demand, and automatically destroyed when its
-// associated WebContents is destroyed.  See content::WebContentsUserData for
-// usage.
-class AudioStreamMonitor
-    : public content::WebContentsUserData<AudioStreamMonitor> {
- public:
-  // Returns true if audio has recently been audible from the tab.  This is
-  // usually called whenever the tab data model is refreshed; but there are
-  // other use cases as well (e.g., the OOM killer uses this to de-prioritize
-  // the killing of tabs making sounds).
-  bool WasRecentlyAudible() const;
-
-  // Starts polling the stream for audio stream power levels using |callback|.
-  typedef base::Callback<std::pair<float, bool>()> ReadPowerAndClipCallback;
-  void StartMonitoringStream(int stream_id,
-                             const ReadPowerAndClipCallback& callback);
-
-  // Stops polling the stream, discarding the internal copy of the |callback|
-  // provided in the call to StartMonitoringStream().
-  void StopMonitoringStream(int stream_id);
-
- private:
-  friend class content::WebContentsUserData<AudioStreamMonitor>;
-  friend class AudioStreamMonitorTest;
-
-  enum {
-    // Desired polling frequency.  Note: If this is set too low, short-duration
-    // "blip" sounds won't be detected.  http://crbug.com/339133#c4
-    kPowerMeasurementsPerSecond = 15,
-
-    // Amount of time to hold a tab indicator on after its last blurt.
-    kHoldOnMilliseconds = 2000
-  };
-
-  // Invoked by content::WebContentsUserData only.
-  explicit AudioStreamMonitor(content::WebContents* contents);
-  virtual ~AudioStreamMonitor();
-
-  // Called by |poll_timer_| to sample the power levels from each of the streams
-  // playing in the tab.
-  void Poll();
-
-  // Compares last known indicator state with what it should be, and triggers UI
-  // updates through |web_contents_| if needed.  When the indicator is turned
-  // on, |off_timer_| is started to re-invoke this method in the future.
-  void MaybeToggle();
-
-  // The WebContents instance instance to receive indicator toggle
-  // notifications.  This pointer should be valid for the lifetime of
-  // AudioStreamMonitor.
-  content::WebContents* const web_contents_;
-
-  // Note: |clock_| is always |&default_tick_clock_|, except during unit
-  // testing.
-  base::DefaultTickClock default_tick_clock_;
-  base::TickClock* const clock_;
-
-  // Confirms single-threaded access in debug builds.
-  base::ThreadChecker thread_checker_;
-
-  // The callbacks to read power levels for each stream.  Only playing (i.e.,
-  // not paused) streams will have an entry in this map.
-  typedef std::map<int, ReadPowerAndClipCallback> StreamPollCallbackMap;
-  StreamPollCallbackMap poll_callbacks_;
-
-  // Records the last time at which sound was audible from any stream.
-  base::TimeTicks last_blurt_time_;
-
-  // Set to true if the last call to MaybeToggle() determined the indicator
-  // should be turned on.
-  bool was_recently_audible_;
-
-  // Calls Poll() at regular intervals while |poll_callbacks_| is non-empty.
-  base::RepeatingTimer<AudioStreamMonitor> poll_timer_;
-
-  // Started only when an indicator is toggled on, to turn it off again in the
-  // future.
-  base::OneShotTimer<AudioStreamMonitor> off_timer_;
-
-  DISALLOW_COPY_AND_ASSIGN(AudioStreamMonitor);
-};
-
-#endif  // CHROME_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_