Refactor how the DeviceMonitor is started.

content/browser/renderer_host/media/media_stream_manager.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // MediaStreamManager is used to open/enumerate media capture devices (video
 // supported now). Call flow:
 // 1. GenerateStream is called when a render process wants to use a capture
 //    device.
 // 2. MediaStreamManager will ask MediaStreamUIController for permission to
 //    use devices and for which device to use.
@@ skipping 120 matching lines @@
   // The request is identified using string returned to the caller.
   std::string OpenDevice(MediaStreamRequester* requester,
                          int render_process_id,
                          int render_view_id,
                          ResourceContext* rc,
                          int page_request_id,
                          const std::string& device_id,
                          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;
   virtual void Closed(MediaStreamType stream_type,
                       int capture_session_id) OVERRIDE;
   virtual void DevicesEnumerated(MediaStreamType stream_type,
                                  const StreamDeviceInfoArray& devices) OVERRIDE;
 
   // Implements base::SystemMonitor::DevicesChangedObserver.
   virtual void OnDevicesChanged(
@@ skipping 166 matching lines @@
 
   bool use_fake_ui_;
   scoped_ptr<FakeMediaStreamUIProxy> fake_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_MANAGER_H_