Cleaned up the WebRtcAudioCapturer a bit.

content/renderer/media/webrtc_audio_device_impl.cc

Index: content/renderer/media/webrtc_audio_device_impl.cc
diff --git a/content/renderer/media/webrtc_audio_device_impl.cc b/content/renderer/media/webrtc_audio_device_impl.cc
index 7519de90a85bac94b98d79171c201c7bdbaea235..239b4cfc435520712d078f2d071e0a0fe611460d 100644
--- a/content/renderer/media/webrtc_audio_device_impl.cc
+++ b/content/renderer/media/webrtc_audio_device_impl.cc
@@ -436,24 +436,47 @@ void WebRtcAudioDeviceImpl::AddAudioCapturer(
   DVLOG(1) << "WebRtcAudioDeviceImpl::AddAudioCapturer()";
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(capturer.get());
-
-  // We only support one microphone today, which means the list can contain
-  // only one capturer with a valid device id.
-  DCHECK(capturer->device_id().empty() || !GetDefaultCapturer());
+  DCHECK(!capturer->device_id().empty());
   base::AutoLock auto_lock(lock_);
+  DCHECK(std::find(capturers_.begin(), capturers_.end(), capturer) ==
+      capturers_.end());
   capturers_.push_back(capturer);
 }
 
+void WebRtcAudioDeviceImpl::RemoveAudioCapturer(
+    const scoped_refptr<WebRtcAudioCapturer>& capturer) {
+  DVLOG(1) << "WebRtcAudioDeviceImpl::AddAudioCapturer()";
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(capturer.get());
+  base::AutoLock auto_lock(lock_);
+  capturers_.remove(capturer);
+}
+
 scoped_refptr<WebRtcAudioCapturer>
 WebRtcAudioDeviceImpl::GetDefaultCapturer() const {
   base::AutoLock auto_lock(lock_);
   for (CapturerList::const_iterator iter = capturers_.begin();
        iter != capturers_.end(); ++iter) {
-    if (!(*iter)->device_id().empty())
-      return *iter;
+    // TODO(xians): It is a bit debatable to determine which one is the default
+    // capturer, the first one or the last one.

[perkj_chrome, 2014/01/14 08:42:40]

And how many can you currently have? You create one per call to GetUSerMEdia? In
that case I would say you should use the last one.

[no longer working on chromium, 2014/01/14 11:10:21]

OK, then lets switch over to the last one.

+    return *iter;
   }
 
   return NULL;
 }
 
+bool WebRtcAudioDeviceImpl::GetAuthorizedDeviceInfoForAudioRenderer(
+    int* session_id,
+    int* output_sample_rate,
+    int* output_frames_per_buffer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // If there is no capturer or there are more than one open capture devices,
+  // return false.
+  if (capturers_.empty() || capturers_.size() > 1)
+    return false;
+
+  return GetDefaultCapturer()->GetPairedOutputParameters(
+      session_id, output_sample_rate, output_frames_per_buffer);
+}
+
 }  // namespace content