Add VideoLayout message.

remoting/proto/control.proto

Index: remoting/proto/control.proto
diff --git a/remoting/proto/control.proto b/remoting/proto/control.proto
index c24343ad6f2e9ae984e72970529f50d895e6d88b..f6922f177ac13d268ef8680759b2ecb00bd2f9ef 100644
--- a/remoting/proto/control.proto
+++ b/remoting/proto/control.proto
@@ -80,4 +80,27 @@ message ExtensionMessage {
   // for each message type; different message types need not shared the same
   // encoding.
   optional string data = 2;
-}
+}
+
+message VideoTrackLayout {
+  // Name of the video track.
+  optional string track_name = 1;
+
+  // Position of the top left corner of the rectangle covered by the video
+  // track in DIPs (device independent pixels).
+  optional int32 position_x = 2;
+  optional int32 position_y = 3;
+
+  // Size of the area covered by the video track in DIPs.
+  optional int32 width = 4;
+  optional int32 height = 5;
+
+  // DPI of the screen.
+  optional int32 x_dpi = 6;
+  optional int32 y_dpi = 7;
+}
+
+message VideoLayout {
+  // Layout for each video track.
+  repeated VideoTrackLayout video_track = 1;
+}