[Mojo Video Capture] Add content_browsertest for exercising video capture

content/browser/renderer_host/media/audio_input_device_manager.cc

Index: content/browser/renderer_host/media/audio_input_device_manager.cc
diff --git a/content/browser/renderer_host/media/audio_input_device_manager.cc b/content/browser/renderer_host/media/audio_input_device_manager.cc
index 890f0e827b4a90ce41023aacf8c724a26228b372..f4309d65f7320c85b08260d3d34619b139dda0e8 100644
--- a/content/browser/renderer_host/media/audio_input_device_manager.cc
+++ b/content/browser/renderer_host/media/audio_input_device_manager.cc
@@ -33,8 +33,7 @@ const int kFirstSessionId = AudioInputDeviceManager::kFakeOpenSessionId + 1;
 
 AudioInputDeviceManager::AudioInputDeviceManager(
     media::AudioManager* audio_manager)
-    : listener_(nullptr),
-      next_capture_session_id_(kFirstSessionId),
+    : next_capture_session_id_(kFirstSessionId),
 #if defined(OS_CHROMEOS)
       keyboard_mic_streams_count_(0),
 #endif
@@ -58,18 +57,19 @@ const StreamDeviceInfo* AudioInputDeviceManager::GetOpenedDeviceInfoById(
 void AudioInputDeviceManager::RegisterListener(
     MediaStreamProviderListener* listener) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  DCHECK(!listener_);
+  DCHECK(listener);
   DCHECK(device_task_runner_);
-  listener_ = listener;
+  listeners_.AddObserver(listener);
 }
 
-void AudioInputDeviceManager::UnregisterListener() {
+void AudioInputDeviceManager::UnregisterListener(
+    MediaStreamProviderListener* listener) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  DCHECK(listener_);
-  listener_ = nullptr;
+  DCHECK(listener);
+  listeners_.RemoveObserver(listener);
 }
 
-int AudioInputDeviceManager::Open(const StreamDeviceInfo& device) {
+int AudioInputDeviceManager::Open(const MediaStreamDevice& device) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   // Generate a new id for this device.
   int session_id = next_capture_session_id_++;
@@ -83,7 +83,7 @@ int AudioInputDeviceManager::Open(const StreamDeviceInfo& device) {
 
 void AudioInputDeviceManager::Close(int session_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  DCHECK(listener_);
+  DCHECK(listeners_.might_have_observers());

[miu, 2017/03/06 21:54:10]

This is weird. Why would a Close() operation require observers be present? Is
the DCHECK() just stating "what would normally be" instead of actually checking
an assumption that would break the impl? If so, it's probably too pedantic and
can be removed. If not, can you add a comment to make it clear what the
assumption is here?

[chfremer, 2017/03/06 23:39:38]

removed

   StreamDeviceList::iterator device = GetDevice(session_id);
   if (device == devices_.end())
     return;
@@ -137,13 +137,13 @@ void AudioInputDeviceManager::UnregisterKeyboardMicStream() {
 #endif
 
 void AudioInputDeviceManager::OpenOnDeviceThread(
-    int session_id, const StreamDeviceInfo& info) {
+    int session_id,
+    const MediaStreamDevice& device) {
   SCOPED_UMA_HISTOGRAM_TIMER(
       "Media.AudioInputDeviceManager.OpenOnDeviceThreadTime");
   DCHECK(IsOnDeviceThread());
 
-  StreamDeviceInfo out(info.device.type, info.device.name, info.device.id, 0, 0,
-                       0);
+  StreamDeviceInfo out(device.type, device.name, device.id, 0, 0, 0);
   out.session_id = session_id;
 
   MediaStreamDevice::AudioDeviceParameters& input_params = out.device.input;
@@ -151,7 +151,7 @@ void AudioInputDeviceManager::OpenOnDeviceThread(
   // Add preferred output device information if a matching output device
   // exists.
   out.device.matched_output_device_id =
-      audio_manager_->GetAssociatedOutputDeviceID(info.device.id);
+      audio_manager_->GetAssociatedOutputDeviceID(device.id);
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kUseFakeDeviceForMediaStream)) {
@@ -177,7 +177,7 @@ void AudioInputDeviceManager::OpenOnDeviceThread(
     // Get the preferred sample rate and channel configuration for the
     // audio device.
     media::AudioParameters params =
-        audio_manager_->GetInputStreamParameters(info.device.id);
+        audio_manager_->GetInputStreamParameters(device.id);
     input_params.sample_rate = params.sample_rate();
     input_params.channel_layout = params.channel_layout();
     input_params.frames_per_buffer = params.frames_per_buffer();
@@ -210,15 +210,15 @@ void AudioInputDeviceManager::OpenedOnIOThread(int session_id,
 
   devices_.push_back(info);
 
-  if (listener_)
-    listener_->Opened(info.device.type, session_id);
+  for (auto& listener : listeners_)
+    listener.Opened(info.device.type, session_id);
 }
 
 void AudioInputDeviceManager::ClosedOnIOThread(MediaStreamType stream_type,
                                                int session_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  if (listener_)
-    listener_->Closed(stream_type, session_id);
+  for (auto& listener : listeners_)
+    listener.Closed(stream_type, session_id);
 }
 
 bool AudioInputDeviceManager::IsOnDeviceThread() const {