Move the device enumerate/open/close work to device thread from IO thread

content/browser/renderer_host/media/media_stream_manager.h

Index: content/browser/renderer_host/media/media_stream_manager.h
diff --git a/content/browser/renderer_host/media/media_stream_manager.h b/content/browser/renderer_host/media/media_stream_manager.h
index 17f863e90fda9b5140ee47983298bb4f17ac1026..c93d7771a7939cb5939a1adaa4e357ecc850da8c 100644
--- a/content/browser/renderer_host/media/media_stream_manager.h
+++ b/content/browser/renderer_host/media/media_stream_manager.h
@@ -30,19 +30,17 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "base/supports_user_data.h"
+#include "base/threading/thread.h"
 #include "content/browser/renderer_host/media/media_stream_provider.h"
 #include "content/browser/renderer_host/media/media_stream_settings_requester.h"
 #include "content/common/media/media_stream_options.h"
 #include "content/common/content_export.h"
+#include "content/public/browser/browser_thread.h"
 
 namespace content {
 class ResourceContext;
 }
 
-namespace media {
-class AudioManager;
-}
-
 namespace media_stream {
 
 class AudioInputDeviceManager;
@@ -62,10 +60,10 @@ class CONTENT_EXPORT MediaStreamManager
   // Returns the MediaStreamManager for the given ResourceContext. If it hasn't
   // been created yet, it will be constructed with the given AudioManager.
   static MediaStreamManager* GetForResourceContext(
-      content::ResourceContext* resource_context,
-      media::AudioManager* audio_manager);
+      content::ResourceContext* resource_context);
+
+  MediaStreamManager();
 
-  explicit MediaStreamManager(media::AudioManager* audio_manager);
   virtual ~MediaStreamManager();
 
   // Used to access VideoCaptureManager.
@@ -132,6 +130,8 @@ class CONTENT_EXPORT MediaStreamManager
   // devices, which is needed for server based testing.
   void UseFakeDevice();
 
+  scoped_refptr<base::MessageLoopProxy> GetMessageLoop();
+
  private:
   // Contains all data needed to keep track of requests.
   struct DeviceRequest;
@@ -149,6 +149,12 @@ class CONTENT_EXPORT MediaStreamManager
   void StartEnumeration(DeviceRequest* new_request,
                         std::string* label);
 
+  // Helper to ensure the device thread before passing to device managers.
+  void EnsureDeviceThread();
+
+  // Device thread shared by VideoCaptureManager and AudioInputDeviceManager.
+  scoped_ptr<base::Thread> device_thread_;
+
   scoped_ptr<MediaStreamDeviceSettings> device_settings_;
   scoped_refptr<VideoCaptureManager> video_capture_manager_;
   scoped_refptr<AudioInputDeviceManager> audio_input_device_manager_;
@@ -160,7 +166,6 @@ class CONTENT_EXPORT MediaStreamManager
   // All non-closed request.
   typedef std::map<std::string, DeviceRequest> DeviceRequests;
   DeviceRequests requests_;
-  media::AudioManager* audio_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamManager);
 };