VideoCapture: migrate last Renderer-->Host msg and start Host-->Renderer migration

content/common/video_capture.mojom

 // Copyright 2016 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.
 
 module content.mojom;
 
+import "gpu/ipc/common/sync_token.mojom";
 import "services/video_capture/public/interfaces/video_capture_device_proxy.mojom";
 import "services/video_capture/public/interfaces/video_capture_format.mojom";
 
 struct VideoCaptureParams {
   video_capture.mojom.VideoCaptureFormat requested_format;
   video_capture.mojom.ResolutionChangePolicy resolution_change_policy;
   video_capture.mojom.PowerLineFrequency power_line_frequency;
 };
 
+enum VideoCaptureState {
+  STARTED,
+  PAUSED,
+  RESUMED,
+  STOPPED,
+  FAILED,
+  ENDED,
+};
+
+// Interface for notifications from Browser/Host back to Renderer/Client. This
+// interface is used between VideoCaptureHost.Start() and Stop().
+interface VideoCaptureObserver {
+  // Gets notigied about a VideoCaptureState update.
+  OnStateChanged(VideoCaptureState state);
+
+// TODO(mcasas): Migrate the rest of the messages, https://crbug.com/651897.
+};
+
 interface VideoCaptureHost {
-  // TODO(mcasas): Migrate the rest of the messages, https://crbug.com/651897.
-
   // Start the |session_id| session with |params|. The video capture will be
   // identified as |device_id|, a new id picked by the renderer process.
-  Start(int32 device_id, int32 session_id, VideoCaptureParams params);
+  // If successful, |observer| will be used for notifications.

[chfremer, 2016/10/10 18:57:19]

With Start() being an asynchronous method without response, how can clients know
whether or not the call was successful?

[mcasas, 2016/10/10 19:39:44]

Actually this is wrongly stated :)  -- in mojo-land, 
this call should always work, since the 
VideoCaptureHost must exist to be called upon. Potential 
errors in its execution should be received via 
VideoCaptureObserver::OnStateChanged().

+  Start(int32 device_id, int32 session_id, VideoCaptureParams params,
+        VideoCaptureObserver observer);
 
   // Closes the video capture specified by |device_id|.
   Stop(int32 device_id);
 
   // Pauses the video capture specified by |device_id|.
   Pause(int32 device_id);
 
   // Resume |device_id| video capture, in |session_id| and with |params|.
   Resume(int32 device_id, int32 session_id, VideoCaptureParams params);
 
   // Requests that the video capturer send a frame "soon" (e.g., to resolve
   // picture loss or quality issues).
   RequestRefreshFrame(int32 device_id);
 
+  // Indicates that a renderer has finished using a previously shared buffer.
+  ReleaseBuffer(int32 device_id, int32 buffer_id,
+                gpu.mojom.SyncToken sync_token,
+                double consumer_resource_utilization);
+
   // Get the formats supported by a device referenced by |session_id|.
   GetDeviceSupportedFormats(int32 device_id, int32 session_id)
     => (array<video_capture.mojom.VideoCaptureFormat> formats_supported);
 
   // Get the format(s) in use by a device referenced by |session_id|.
   GetDeviceFormatsInUse(int32 device_id, int32 session_id)
     => (array<video_capture.mojom.VideoCaptureFormat> formats_in_use);
 };