Use AudioStreamMonitor to control power save blocking.

content/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_
+#ifndef CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
+#define CONTENT_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;
 }
 
+namespace content {
+class PowerSaveBlocker;
+
 // 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> {
+//
+// AudioStreamMonitor will additionally create a PowerSaveBlocker to prevent app
+// suspension when audible audio is being produced.
+class CONTENT_EXPORT AudioStreamMonitor
+    : public 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|.
+  // Starts or stops audio level monitoring respectively for the stream owned by
+  // the specified renderer.  Safe to call from any thread.
+  //
+  // The callback returns the current power level (in dBFS units) and the clip
+  // status (true if any part of the audio signal has clipped since the last
+  // callback run).
   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);
+  static void StartMonitoringStream(
+      int render_process_id,
+      int render_frame_id,
+      int stream_id,
+      const ReadPowerAndClipCallback& read_power_callback);
+  static void StopMonitoringStream(int render_process_id,
+                                   int render_frame_id,
+                                   int stream_id);
 
  private:
-  friend class content::WebContentsUserData<AudioStreamMonitor>;
+  friend class 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);
+  // Invoked by WebContentsUserData only.
+  explicit AudioStreamMonitor(WebContents* contents);
   virtual ~AudioStreamMonitor();
 
+  // Helper methods for starting and stopping monitoring which lookup the
+  // identified renderer and forward calls to the correct AudioStreamMonitor.
+  static void StartMonitoringHelper(
+      int render_process_id,
+      int render_frame_id,
+      int stream_id,
+      const ReadPowerAndClipCallback& read_power_callback);
+  static void StopMonitoringHelper(int render_process_id,
+                                   int render_frame_id,
+                                   int stream_id);
+
+  // Starts polling the stream for audio stream power levels using |callback|.
+  void StartMonitoringStreamOnUIThread(
+      int stream_id,
+      const ReadPowerAndClipCallback& callback);
+
+  // Stops polling the stream, discarding the internal copy of the |callback|
+  // provided in the call to StartMonitoringStream().
+  void StopMonitoringStreamOnUIThread(int stream_id);
+
   // 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_;
+  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_;
 
+  // Prevent app suspension when audio is active.
+  scoped_ptr<PowerSaveBlocker> blocker_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioStreamMonitor);
 };
 
-#endif  // CHROME_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_