Refactor how the MediaStreamManager::DeviceMonitor is started.

Review URL: https://codereview.chromium.org/57913002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238409 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/media/media_devices_monitor.cc

@@ -12,10 +12,7 @@ namespace content {
 namespace {
 void EnsureMonitorCaptureDevicesInternal(
     MediaStreamManager* media_stream_manager) {
-  // TODO(perkj): The argument list suggests that this is the wrong design. Can
-  // we add a separate method for device monitoring?
-  media_stream_manager->EnumerateDevices(
-      NULL, -1, -1, NULL, -1, MEDIA_DEVICE_AUDIO_CAPTURE, GURL());
+  media_stream_manager->EnsureDeviceMonitorStarted();
 }
 }
 

content/browser/renderer_host/media/media_stream_manager.cc

@@ -413,18 +413,10 @@ std::string MediaStreamManager::EnumerateDevices(
     MediaStreamType type,
     const GURL& security_origin) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK(requester);
   DCHECK(type == MEDIA_DEVICE_AUDIO_CAPTURE ||
          type == MEDIA_DEVICE_VIDEO_CAPTURE);
 
-  // When the requester is NULL, the request is made by the UI to ensure MSM
-  // starts monitoring devices.
-  if (!requester) {
-    if (!monitoring_started_)
-      StartMonitoring();
-
-    return std::string();
-  }
-
   // Create a new request.
   StreamOptions options;
   if (type == MEDIA_DEVICE_AUDIO_CAPTURE) {
@@ -534,6 +526,12 @@ std::string MediaStreamManager::OpenDevice(
   return label;
 }
 
+void MediaStreamManager::EnsureDeviceMonitorStarted() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  if (!monitoring_started_)
+    StartMonitoring();
+}
+
 void MediaStreamManager::StopRemovedDevices(
     const StreamDeviceInfoArray& old_devices,
     const StreamDeviceInfoArray& new_devices) {

content/browser/renderer_host/media/media_stream_manager.h

@@ -138,6 +138,10 @@ class CONTENT_EXPORT MediaStreamManager
                          MediaStreamType type,
                          const GURL& security_origin);
 
+  // Called by UI to make sure the device monitor is started so that UI receive
+  // notifications about device changes.
+  void EnsureDeviceMonitorStarted();
+
   // Implements MediaStreamProviderListener.
   virtual void Opened(MediaStreamType stream_type,
                       int capture_session_id) OVERRIDE;