Makes resolving ids work correctly in new world

components/mus/ws/server_window_delegate.h

Index: components/mus/ws/server_window_delegate.h
diff --git a/components/mus/ws/server_window_delegate.h b/components/mus/ws/server_window_delegate.h
index 549cdf31ebf0e397e54771679b838632a0791c37..760d45a6e308433af7a07e0285ee1fd237789821 100644
--- a/components/mus/ws/server_window_delegate.h
+++ b/components/mus/ws/server_window_delegate.h
@@ -7,6 +7,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "components/mus/public/interfaces/mus_constants.mojom.h"
+#include "components/mus/public/interfaces/window_tree.mojom.h"
 
 namespace mus {
 
@@ -14,6 +15,7 @@ class SurfacesState;
 
 namespace ws {
 
+struct ClientWindowId;
 class ServerWindow;
 struct WindowId;
 
@@ -32,6 +34,17 @@ class ServerWindowDelegate {
   // appropriate time, which may be synchronously.
   virtual void ScheduleSurfaceDestruction(ServerWindow* window) = 0;
 
+  // Used to resolve a reference to a Window by ClientWindowId in submitted
+  // frames. When the client owning |ancestor| (or the client embedded at
+  // |ancestor|) submits a frame the frame may referenced child windows. The
+  // reference is done using an id that is only known to the client. This
+  // function resolves the id into the appropriate window, or null if a window
+  // can't be found.
+  virtual ServerWindow* FindWindowForSurface(
+      const ServerWindow* ancestor,
+      mojom::SurfaceType surface_type,
+      const ClientWindowId& client_window_id) = 0;
+
  protected:
   virtual ~ServerWindowDelegate() {}
 };