Reverted the code for the non-interactive audible tab notification

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 b3cbf16f4d3d63192d9acc60fc2072eb4be97beb..bf5de689bb0866ce6dd0eccbcd922929834791d4 100644
--- a/content/browser/media/audio_stream_monitor.h
+++ b/content/browser/media/audio_stream_monitor.h
@@ -14,7 +14,6 @@
 #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"
 
@@ -24,6 +23,8 @@ 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
@@ -32,23 +33,23 @@ namespace content {
 // to turn on/off repeatedly and annoy the user.  AudioStreamMonitor sends UI
 // update notifications only when needed, but may be queried at any time.
 //
-class CONTENT_EXPORT AudioStreamMonitor : public AudioStateProvider {
+// Each WebContentsImpl owns an AudioStreamMonitor.
+class CONTENT_EXPORT AudioStreamMonitor {
  public:
   explicit AudioStreamMonitor(WebContents* contents);
-  ~AudioStreamMonitor() override;
+  ~AudioStreamMonitor();
 
   // Indicates if audio stream monitoring is available.  It's only available if
   // AudioOutputController can and will monitor output power levels.
-  bool IsAudioStateAvailable() const override;
-
-  // This provider is a monitor, the method returns |this|.
-  AudioStreamMonitor* audio_stream_monitor() override;
+  static bool monitoring_available() {
+    return media::AudioOutputController::will_monitor_audio_levels();
+  }
 
   // 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 override;
+  bool WasRecentlyAudible() const;
 
   // Starts or stops audio level monitoring respectively for the stream owned by
   // the specified renderer.  Safe to call from any thread.
@@ -66,6 +67,10 @@ class CONTENT_EXPORT AudioStreamMonitor : public AudioStateProvider {
                                    int render_frame_id,
                                    int stream_id);
 
+  void set_was_recently_audible_for_testing(bool value) {
+    was_recently_audible_ = value;
+  }
+
  private:
   friend class AudioStreamMonitorTest;
 
@@ -108,6 +113,10 @@ class CONTENT_EXPORT AudioStreamMonitor : public AudioStateProvider {
   // on, |off_timer_| is started to re-invoke this method in the future.
   void MaybeToggle();
 
+  // 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_;
@@ -125,6 +134,10 @@ class CONTENT_EXPORT AudioStreamMonitor : public AudioStateProvider {
   // 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_;