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

content/browser/media/audio_stream_monitor.cc

 // 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.
 
 #include "content/browser/media/audio_stream_monitor.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/invalidate_type.h"
 #include "content/public/browser/render_frame_host.h"
 
 namespace content {
 
 namespace {
 
 AudioStreamMonitor* AudioStreamMonitorFromRenderFrame(int render_process_id,
                                                       int render_frame_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   WebContentsImpl* const web_contents =
       static_cast<WebContentsImpl*>(WebContents::FromRenderFrameHost(
           RenderFrameHost::FromID(render_process_id, render_frame_id)));
   return web_contents ? web_contents->audio_stream_monitor() : NULL;
 }
 
 }  // namespace
 
-AudioStreamMonitor::AudioStreamMonitor(WebContents* contents)
-    : web_contents_(contents),
+AudioStreamMonitor::AudioStreamMonitor(const AudibleChangeCallback& callback)
+    : audible_change_callback_(callback),
       clock_(&default_tick_clock_),
       was_recently_audible_(false) {
-  DCHECK(web_contents_);
+  DCHECK(!audible_change_callback_.is_null());
 }
 
 AudioStreamMonitor::~AudioStreamMonitor() {}
 
 bool AudioStreamMonitor::WasRecentlyAudible() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return was_recently_audible_;
 }
 
 // static
@@ skipping 95 matching lines @@
 
 void AudioStreamMonitor::MaybeToggle() {
   const bool indicator_was_on = was_recently_audible_;
   const base::TimeTicks off_time =
       last_blurt_time_ + base::TimeDelta::FromMilliseconds(kHoldOnMilliseconds);
   const base::TimeTicks now = clock_->NowTicks();
   const bool should_indicator_be_on = now < off_time;
 
   if (should_indicator_be_on != indicator_was_on) {
     was_recently_audible_ = should_indicator_be_on;
-    web_contents_->NotifyNavigationStateChanged(INVALIDATE_TYPE_TAB);
+    audible_change_callback_.Run(was_recently_audible_);
   }
 
   if (!should_indicator_be_on) {
     off_timer_.Stop();
   } else if (!off_timer_.IsRunning()) {
     off_timer_.Start(
         FROM_HERE,
         off_time - now,
         base::Bind(&AudioStreamMonitor::MaybeToggle, base::Unretained(this)));
   }
 }
 
 }  // namespace content