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

content/common/video_capture.mojom

Index: content/common/video_capture.mojom
diff --git a/content/common/video_capture.mojom b/content/common/video_capture.mojom
index bd89d463b02d5fd46f4855f214520c7a6a722779..a7fba1fbbc45463a3ffc680d8ba51e4833931aca 100644
--- a/content/common/video_capture.mojom
+++ b/content/common/video_capture.mojom
@@ -4,6 +4,7 @@
 
 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";
 
@@ -13,12 +14,30 @@ struct VideoCaptureParams {
   video_capture.mojom.PowerLineFrequency power_line_frequency;
 };
 
-interface VideoCaptureHost {
-  // TODO(mcasas): Migrate the rest of the messages, https://crbug.com/651897.
+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 {
   // 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);
@@ -33,6 +52,11 @@ interface VideoCaptureHost {
   // 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);