Propagate audible state from player to the containing tab

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 CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
 #define CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
 
 #include <map>
 #include <utility>
 
 #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 "build/build_config.h"
+#include "content/browser/media/audio_state_provider.h"
 #include "content/common/content_export.h"
 #include "media/audio/audio_output_controller.h"
 
 namespace base {
 class TickClock;
 }
 
 namespace content {
-class WebContents;
 
 // 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.
 //
-// Each WebContentsImpl owns an AudioStreamMonitor.
-class CONTENT_EXPORT AudioStreamMonitor {
+class CONTENT_EXPORT AudioStreamMonitor : public AudioStateProvider {
  public:
   explicit AudioStreamMonitor(WebContents* contents);
-  ~AudioStreamMonitor();
+  ~AudioStreamMonitor() override;
 
   // Indicates if audio stream monitoring is available.  It's only available if
   // AudioOutputController can and will monitor output power levels.
-  static bool monitoring_available() {
-    return media::AudioOutputController::will_monitor_audio_levels();
-  }
+  bool IsAudioStateAvailable() const override;
+
+  // This provider is a monitor, the method returns |this|.
+  AudioStreamMonitor* audio_stream_monitor() override;
 
   // 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;
+  bool WasRecentlyAudible() const override;
 
   // 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).  |stream_id| must be unique within a |render_process_id|.
   typedef base::Callback<std::pair<float, bool>()> ReadPowerAndClipCallback;
   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);
 
-  void set_was_recently_audible_for_testing(bool value) {
-    was_recently_audible_ = value;
-  }
-
  private:
   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
@@ skipping 22 matching lines @@
 
   // 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.
-  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::pair<int, int> StreamID;
   typedef std::map<StreamID, 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);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_