Add metrics regarding concurrent audible tabs in Chromium.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 1161 matching lines @@
 
 void WebContentsImpl::NotifyNavigationStateChanged(
     InvalidateTypes changed_flags) {
   // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466285
   // is fixed.
   tracked_objects::ScopedTracker tracking_profile(
       FROM_HERE_WITH_EXPLICIT_FUNCTION(
           "466285 WebContentsImpl::NotifyNavigationStateChanged"));
   // Notify the media observer of potential audibility changes.
   if (changed_flags & INVALIDATE_TYPE_TAB) {
-    media_web_contents_observer_->MaybeUpdateAudibleState(
-        AudioStreamMonitor::monitoring_available() && WasRecentlyAudible());
+    media_web_contents_observer_->MaybeUpdateAudibleState();
   }
 
   if (delegate_)
     delegate_->NavigationStateChanged(this, changed_flags);
 }
 
 base::TimeTicks WebContentsImpl::GetLastActiveTime() const {
   return last_active_time_;
 }
 
@@ skipping 3550 matching lines @@
     const WebContentsObserver::MediaPlayerId& id) {
   FOR_EACH_OBSERVER(WebContentsObserver, observers_, MediaStartedPlaying(id));
 }
 
 void WebContentsImpl::MediaStoppedPlaying(
     const WebContentsObserver::MediaPlayerId& id) {
   FOR_EACH_OBSERVER(WebContentsObserver, observers_, MediaStoppedPlaying(id));
 }
 
 }  // namespace content