Add metrics regarding concurrent audible tabs in Chromium.

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"
@@ skipping 12 matching lines @@
           RenderFrameHost::FromID(render_process_id, render_frame_id)));
 
   return web_contents ? web_contents->audio_stream_monitor() : nullptr;
 }
 
 }  // namespace
 
 AudioStreamMonitor::AudioStreamMonitor(WebContents* contents)
     : web_contents_(contents),
       clock_(&default_tick_clock_),
-      was_recently_audible_(false)
+      was_recently_audible_(false),
+      is_audible_(false)
 {
   DCHECK(web_contents_);
 }
 
 AudioStreamMonitor::~AudioStreamMonitor() {}
 
 bool AudioStreamMonitor::WasRecentlyAudible() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return was_recently_audible_;
 }
 
+bool AudioStreamMonitor::IsCurrentlyAudible() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return is_audible_;
+}
+
 // static
 void AudioStreamMonitor::StartMonitoringStream(
     int render_process_id,
     int render_frame_id,
     int stream_id,
     const ReadPowerAndClipCallback& read_power_callback) {
   if (!monitoring_available())
     return;
   BrowserThread::PostTask(BrowserThread::UI,
                           FROM_HERE,
@@ skipping 62 matching lines @@
 
 void AudioStreamMonitor::StopMonitoringStreamOnUIThread(int render_process_id,
                                                         int stream_id) {
   DCHECK(thread_checker_.CalledOnValidThread());
   poll_callbacks_.erase(StreamID(render_process_id, stream_id));
   if (poll_callbacks_.empty())
     poll_timer_.Stop();
 }
 
 void AudioStreamMonitor::Poll() {
+  bool was_audible = is_audible_;
+  is_audible_ = false;
+
   for (StreamPollCallbackMap::const_iterator it = poll_callbacks_.begin();
        it != poll_callbacks_.end();
        ++it) {
     // TODO(miu): A new UI for delivering specific power level and clipping
     // information is still in the works.  For now, we throw away all
     // information except for "is it audible?"
     const float power_dbfs = it->second.Run().first;
     const float kSilenceThresholdDBFS = -72.24719896f;
+
     if (power_dbfs >= kSilenceThresholdDBFS) {
       last_blurt_time_ = clock_->NowTicks();
+      is_audible_ = true;
       MaybeToggle();
       break;  // No need to poll remaining streams.
     }
   }
+
+  if (is_audible_ != was_audible)
+    web_contents_->NotifyNavigationStateChanged(INVALIDATE_TYPE_TAB);
 }
 
 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);
   }
 
   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