[AudioStreamMonitor] Adds API to collect frame-level audibility.

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/macros.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 "base/tuple.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "media/audio/audio_output_controller.h"
 
 namespace base {
 class TickClock;
 }
 
 namespace content {
 
@@ skipping 77 matching lines @@
       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 render_process_id,
+      int render_frame_id,
       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 render_process_id, int stream_id);
+  void StopMonitoringStreamOnUIThread(int render_process_id,
+                                      int render_frame_id,
+                                      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();
 
   // Helper functions to track number of active streams when power level
   // monitoring is not available.
   void OnStreamAdded();
   void OnStreamRemoved();
 
   // The WebContents 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.
-  using StreamID = std::pair<int, int>;
+  // StreamID is formed by <render_process_id, render_frame_id, stream_id>
+  using StreamID = std::tuple<int, int, int>;

[DaleCurtis, 2017/06/22 00:35:55]

This would be clearer as:

struct StreamID {
  int render_process_id;
  int render_frame_id;
  int stream_id;
};

You'll still be able to initialize it the same way (as POD type you can use =
{1,2,3}), but now we have named fields for legibility.

[lpy, 2017/06/22 02:28:52]

Done.

   using StreamPollCallbackMap = std::map<StreamID, ReadPowerAndClipCallback>;
   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_;
 
   // Whether the WebContents is currently audible.
   bool is_audible_;
 
   // Calls Poll() at regular intervals while |poll_callbacks_| is non-empty.
   base::RepeatingTimer poll_timer_;
 
   // Started only when an indicator is toggled on, to turn it off again in the
   // future.
   base::OneShotTimer off_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioStreamMonitor);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_