Mus: Delete unused Mandoline Surfaces code

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 caae817da9ff871de5e3e7509e5ec87dc05b2db4..24d6bbd0daae80879a6a661cdb8de67e69507a38 100644
--- a/components/mus/ws/server_window_delegate.h
+++ b/components/mus/ws/server_window_delegate.h
@@ -35,17 +35,6 @@ 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() {}
 };