Make tab audible and muted states and cause available for an extension API

content/browser/media/audio_stream_monitor.h

Index: content/browser/media/audio_stream_monitor.h
diff --git a/content/browser/media/audio_stream_monitor.h b/content/browser/media/audio_stream_monitor.h
index d1a32d5f857b05925f884ef64d834e673c8c5f29..cf8f15587e5f11fc6052b106ad7a52dc20b93369 100644
--- a/content/browser/media/audio_stream_monitor.h
+++ b/content/browser/media/audio_stream_monitor.h
@@ -22,7 +22,6 @@ 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
@@ -35,7 +34,9 @@ class WebContents;
 // Each WebContentsImpl owns an AudioStreamMonitor.
 class CONTENT_EXPORT AudioStreamMonitor {
  public:
-  explicit AudioStreamMonitor(WebContents* contents);
+  using AudibleChangeCallback = base::Callback<void(bool)>;
+
+  explicit AudioStreamMonitor(const AudibleChangeCallback& callback);
   ~AudioStreamMonitor();
 
   // Indicates if audio stream monitoring is available.  It's only available if
@@ -112,10 +113,8 @@ class CONTENT_EXPORT AudioStreamMonitor {
   // 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_;
+  // The Callback to run to receive indicator toggle notifications.
+  const AudibleChangeCallback audible_change_callback_;
 
   // Note: |clock_| is always |&default_tick_clock_|, except during unit
   // testing.