WebContentsAudioMuter: Mute all audio output from a WebContentsImpl.

content/browser/media/capture/web_contents_audio_input_stream.cc

 // Copyright (c) 2013 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/capture/web_contents_audio_input_stream.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 56 matching lines @@
   virtual ~Impl();
 
   // Notifies the consumer callback that the stream is now dead.
   void ReportError();
 
   // (Re-)Start/Stop mirroring by posting a call to AudioMirroringManager on the
   // IO BrowserThread.
   void StartMirroring();
   void StopMirroring();
 
+  // Invoked on the UI thread to make sure WebContents muting is turned off for
+  // successful audio capture.
+  void UnmuteWebContentsAudio();
+
   // AudioMirroringManager::MirroringDestination implementation
   virtual void QueryForMatches(
       const std::set<SourceFrameRef>& candidates,
       const MatchesCallback& results_callback) OVERRIDE;
   void QueryForMatchesOnUIThread(const std::set<SourceFrameRef>& candidates,
                                  const MatchesCallback& results_callback);
   virtual media::AudioOutputStream* AddInput(
       const media::AudioParameters& params) OVERRIDE;
 
   // Callback which is run when |stream| is closed.  Deletes |stream|.
@@ skipping 80 matching lines @@
   if (is_target_lost_) {
     ReportError();
     callback_ = NULL;
     return;
   }
 
   state_ = MIRRORING;
   mixer_stream_->Start(callback);
 
   StartMirroring();
+
+  // WebContents audio muting is implemented as audio capture to nowhere.
+  // Unmuting will stop that audio capture, allowing AudioMirroringManager to
+  // divert audio capture to here.
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&Impl::UnmuteWebContentsAudio, this));
 }
 
 void WebContentsAudioInputStream::Impl::Stop() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (state_ != MIRRORING)
     return;
 
   state_ = OPENED;
 
@@ skipping 41 matching lines @@
   DCHECK(thread_checker_.CalledOnValidThread());
 
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&AudioMirroringManager::StopMirroring,
                  base::Unretained(mirroring_manager_),
                  make_scoped_refptr(this)));
 }
 
+void WebContentsAudioInputStream::Impl::UnmuteWebContentsAudio() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  WebContents* const contents = tracker_->web_contents();
+  if (contents)
+    contents->SetAudioMuted(false);
+}
+
 void WebContentsAudioInputStream::Impl::QueryForMatches(
     const std::set<SourceFrameRef>& candidates,
     const MatchesCallback& results_callback) {
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
       base::Bind(&Impl::QueryForMatchesOnUIThread,
                  this,
                  candidates,
                  media::BindToCurrentLoop(results_callback)));
@@ skipping 117 matching lines @@
 
 void WebContentsAudioInputStream::SetAutomaticGainControl(bool enabled) {
   impl_->mixer_stream()->SetAutomaticGainControl(enabled);
 }
 
 bool WebContentsAudioInputStream::GetAutomaticGainControl() {
   return impl_->mixer_stream()->GetAutomaticGainControl();
 }
 
 }  // namespace content