Add VideoLayout message.

remoting/protocol/video_stream.h

Index: remoting/protocol/video_stream.h
diff --git a/remoting/protocol/video_stream.h b/remoting/protocol/video_stream.h
index f81db85f81c2fce065ca2e9dd50c97b3f276ed94..3f7a27bd5d6aa13e2ede033a6784cdfaae41802b 100644
--- a/remoting/protocol/video_stream.h
+++ b/remoting/protocol/video_stream.h
@@ -13,6 +13,7 @@
 
 namespace webrtc {
 class DesktopSize;
+class DesktopVector;
 }  // namespace webrtc
 
 namespace remoting {
@@ -20,8 +21,11 @@ namespace protocol {
 
 class VideoStream {
  public:
-  // Callback used to notify about screen size changes.
-  typedef base::Callback<void(const webrtc::DesktopSize& size)> SizeCallback;
+  // Callback used to notify about screen size changes. The size must be
+  // specified in DIPs.
+  typedef base::Callback<void(const webrtc::DesktopSize& size,
+                              const webrtc::DesktopVector& dpi)>
+      SizeCallback;
 
   VideoStream() {}
   virtual ~VideoStream() {}