Increment/Decrement capturer count when starts/stops audio capturing.

content/browser/media/capture/web_contents_audio_input_stream.cc

Index: content/browser/media/capture/web_contents_audio_input_stream.cc
diff --git a/content/browser/media/capture/web_contents_audio_input_stream.cc b/content/browser/media/capture/web_contents_audio_input_stream.cc
index 348af609ed0ce2f46b648fed24496a9108b8131e..b9f15e6cd0607142c1a8194363f36a01239c06a0 100644
--- a/content/browser/media/capture/web_contents_audio_input_stream.cc
+++ b/content/browser/media/capture/web_contents_audio_input_stream.cc
@@ -78,6 +78,10 @@ class WebContentsAudioInputStream::Impl
   void StartMirroring();
   void StopMirroring();
 
+  // Increment/decrement the capturer count on the UI BrowserThread.
+  void IncrementCapturerCount();
+  void DecrementCapturerCount();
+
   // Invoked on the UI thread to make sure WebContents muting is turned off for
   // successful audio capture.
   void UnmuteWebContentsAudio();
@@ -165,14 +169,22 @@ bool WebContentsAudioInputStream::Impl::Open() {
     return false;
 
   state_ = OPENED;
-
   tracker_->Start(
       initial_render_process_id_, initial_main_render_frame_id_,
       base::Bind(&Impl::OnTargetChanged, this));
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                          base::Bind(&Impl::IncrementCapturerCount, this));
 
   return true;
 }
 
+void WebContentsAudioInputStream::Impl::IncrementCapturerCount() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  if (WebContents* contents = tracker_->web_contents())
+    contents->IncrementCapturerCount(gfx::Size());
+}
+
 void WebContentsAudioInputStream::Impl::Start(AudioInputCallback* callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(callback);
@@ -222,6 +234,8 @@ void WebContentsAudioInputStream::Impl::Close() {
 
   if (state_ == OPENED) {
     state_ = CONSTRUCTED;
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                            base::Bind(&Impl::DecrementCapturerCount, this));
     tracker_->Stop();
     mixer_stream_->Close();
   }
@@ -230,6 +244,13 @@ void WebContentsAudioInputStream::Impl::Close() {
   state_ = CLOSED;
 }
 
+void WebContentsAudioInputStream::Impl::DecrementCapturerCount() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  if (WebContents* contents = tracker_->web_contents())
+    contents->DecrementCapturerCount();
+}
+
 void WebContentsAudioInputStream::Impl::ReportError() {
   DCHECK(thread_checker_.CalledOnValidThread());