Revert of Revert of Propagate audible state from player to the containing tab"

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;
+
+  if (!web_contents)
+    return nullptr;
+
+  AudioStateProvider* audio_provider = web_contents->audio_state_provider();
+  return audio_provider ? audio_provider->audio_stream_monitor() : nullptr;
 }
 
 }  // namespace
 
 AudioStreamMonitor::AudioStreamMonitor(WebContents* contents)
-    : web_contents_(contents),
-      clock_(&default_tick_clock_),
-      was_recently_audible_(false) {
-  DCHECK(web_contents_);
+    : AudioStateProvider(contents),
+      clock_(&default_tick_clock_)
+{
 }
 
 AudioStreamMonitor::~AudioStreamMonitor() {}
 
+bool AudioStreamMonitor::IsAudioStateAvailable() const {
+  return media::AudioOutputController::will_monitor_audio_levels();
+}
+
+// This provider is the monitor.
+AudioStreamMonitor* AudioStreamMonitor::audio_stream_monitor() {
+  return this;
+}
+
 bool AudioStreamMonitor::WasRecentlyAudible() const {
   DCHECK(thread_checker_.CalledOnValidThread());
-  return was_recently_audible_;
+  return AudioStateProvider::WasRecentlyAudible();
 }
 
 // static
 void AudioStreamMonitor::StartMonitoringStream(
     int render_process_id,
     int render_frame_id,
     int stream_id,
     const ReadPowerAndClipCallback& read_power_callback) {
-  if (!monitoring_available())
+  if (!media::AudioOutputController::will_monitor_audio_levels())
     return;
   BrowserThread::PostTask(BrowserThread::UI,
                           FROM_HERE,
                           base::Bind(&StartMonitoringHelper,
                                      render_process_id,
                                      render_frame_id,
                                      stream_id,
                                      read_power_callback));
 }
 
 // static
 void AudioStreamMonitor::StopMonitoringStream(int render_process_id,
                                               int render_frame_id,
                                               int stream_id) {
-  if (!monitoring_available())
+  if (!media::AudioOutputController::will_monitor_audio_levels())
     return;
   BrowserThread::PostTask(BrowserThread::UI,
                           FROM_HERE,
                           base::Bind(&StopMonitoringHelper,
                                      render_process_id,
                                      render_frame_id,
                                      stream_id));
 }
 
 // static
@@ skipping 56 matching lines @@
     const float kSilenceThresholdDBFS = -72.24719896f;
     if (power_dbfs >= kSilenceThresholdDBFS) {
       last_blurt_time_ = clock_->NowTicks();
       MaybeToggle();
       break;  // No need to poll remaining streams.
     }
   }
 }
 
 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);
-  }
+  Notify(should_indicator_be_on);
 
   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