[Mojo Video Capture] Fix VideoCaptureManager exposing implementation details to clients

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 7b583f3d925c93fb2262dfe584cde66183032842..32c1ba304aa19c817d2979fc3b973188e7c6b311 100644
--- a/content/browser/renderer_host/media/media_stream_manager.h
+++ b/content/browser/renderer_host/media/media_stream_manager.h
@@ -49,6 +49,7 @@
 
 namespace media {
 class AudioSystem;
+class VideoCaptureSystem;
 }
 
 namespace url {
@@ -85,7 +86,18 @@ class CONTENT_EXPORT MediaStreamManager
   // logging from webrtcLoggingPrivate API. Safe to call from any thread.
   static void SendMessageToNativeLog(const std::string& message);
 
-  explicit MediaStreamManager(media::AudioSystem* audio_system);
+  static std::unique_ptr<MediaStreamManager> CreateWithDefaults(

[miu, 2017/04/03 21:31:23]

Perhaps include a comment about threading/task-runners to be assumed here?

[chfremer, 2017/04/04 21:59:32]

I wouldn't know what to say here. As a reader, what kind of information would
you be looking for here that would not have been given in the class-level
description?

I don't feel I understand the class MediaStreamManager enough to attempt
explaining it in a class-level comment.

+      media::AudioSystem* audio_system);
+
+  static std::unique_ptr<MediaStreamManager>
+  CreateWithCustomVideoCaptureDeviceTaskRunner(

[miu, 2017/04/03 21:31:23]

Looks like nothing calls this. So, can we delete it?

[chfremer, 2017/04/04 21:59:32]

Done.

+      media::AudioSystem* audio_system,
+      scoped_refptr<base::SingleThreadTaskRunner> device_task_runner);
+
+  static std::unique_ptr<MediaStreamManager> CreateWithCustomVideoCaptureSystem(
+      media::AudioSystem* audio_system,
+      std::unique_ptr<media::VideoCaptureSystem> video_capture_system,
+      scoped_refptr<base::SingleThreadTaskRunner> device_task_runner);
 
   ~MediaStreamManager() override;
 
@@ -277,9 +289,14 @@ class CONTENT_EXPORT MediaStreamManager
   using LabeledDeviceRequest = std::pair<std::string, DeviceRequest*>;
   using DeviceRequests = std::list<LabeledDeviceRequest>;
 
-  // Initializes the device managers on IO thread.  Auto-starts the device
-  // thread and registers this as a listener with the device managers.
-  void InitializeDeviceManagersOnIOThread();
+  explicit MediaStreamManager(media::AudioSystem* audio_system);
+  void InitializeWithDefaults();
+  void InitializeWithCustomVideoCaptureDeviceTaskRunner(
+      scoped_refptr<base::SingleThreadTaskRunner> device_task_runner);
+  void InitializeWithCustomVideoCaptureSystem(
+      std::unique_ptr<media::VideoCaptureSystem> video_capture_system,
+      scoped_refptr<base::SingleThreadTaskRunner> device_task_runner);
+  void PerformCommonInitializationRoutines();
 
   // |output_parameters| contains real values only if the request requires it.
   void HandleAccessRequestResponse(