Refactor how the DeviceMonitor is started.

content/browser/renderer_host/media/media_stream_manager.cc

Index: content/browser/renderer_host/media/media_stream_manager.cc
diff --git a/content/browser/renderer_host/media/media_stream_manager.cc b/content/browser/renderer_host/media/media_stream_manager.cc
index a3b9358f42208ca5db6e687db78ab07e8a490dc1..30aa7e5f60f32fd88534f4977da94b6152a912a5 100644
--- a/content/browser/renderer_host/media/media_stream_manager.cc
+++ b/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) {