Propagate audible state from player to the containing tab

content/browser/media/audio_state_provider.h

+// Copyright 2015 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_STATE_PROVIDER_H_
+#define CONTENT_BROWSER_MEDIA_AUDIO_STATE_PROVIDER_H_
+
+namespace content {
+class WebContents;
+class AudioStreamMonitor;
+
+// This class is associated with a WebContents, and maintains the audible
+// state regarding all the players in it.
+// The audible state is true if at least one player is playing a sound.
+// Whenever the audible state of the WebContents as a whole changes, this
+// class sends a notification to it.
+//
+// Each WebContentsImpl owns an AudioStateProvider
+class AudioStateProvider {
+ public:
+  explicit AudioStateProvider(WebContents* web_contents);
+  virtual ~AudioStateProvider() {}
+
+  // Indicates whether this service is available on the system.
+  static bool audio_state_available();

[Tima Vaisburd, 2015/02/24 03:06:50]

Does it have to be static?

[qinmin, 2015/02/24 18:02:19]

I think static is fine, but would prefer this to be renamed to
IsAudioStateAvailable() as this is not inline.

[no sievers, 2015/02/25 21:22:04]

'virtual' would maybe be a tiny bit nicer since it avoids the #ifdef in the
implementation, and moves that to the platform-specific impl file instead. And
also since you do the same thing for audio_stream_monitor().

[Tima Vaisburd, 2015/02/28 03:16:05]

Made pure virtual method IsAudioStateAvailable(). However, it is used on
WebContentsImpl destructor via MaybeReleasePowerSaveBlockers(), I moved the
member up, please advise.

+
+  // If this provider use monitoring (i.e. measure the signal),

[qinmin, 2015/02/24 18:02:19]

nit: s/use/uses/

[Tima Vaisburd, 2015/02/28 03:16:05]

Done.

+  // return its monitor.
+  virtual AudioStreamMonitor* audio_stream_monitor() = 0;

[no sievers, 2015/02/25 21:22:04]

Only used for testing, i.e. GetAudioStreamMonitorForTesting()?

[Tima Vaisburd, 2015/02/28 03:16:05]

It is also used in AudioStreamMonitorFromRenderFrame() in
audio_stream_monitor.cc, I kept the old name.

+
+  // Returns true if the WebContents is playing or has recently been
+  // playing the sound.
+  virtual bool WasRecentlyAudible() const;
+
+  void set_was_recently_audible_for_testing(bool value) {
+    was_recently_audible_ = value;
+  }
+
+ protected:
+  // Notify WebContents that the audio state has changed.
+  void Notify(bool new_state);
+
+  // The WebContents instance instance to receive indicator toggle
+  // notifications.  This pointer should be valid for the lifetime of
+  // AudioStreamMonitor.
+  WebContents* const web_contents_;
+
+  // The audio state that is being maintained
+  bool  was_recently_audible_;

[no sievers, 2015/02/25 21:22:04]

nit: extra space

[Tima Vaisburd, 2015/02/28 03:16:05]

Done.

+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_AUDIO_STATE_PROVIDER_H_