Make aura work with mus

ui/aura/window_delegate.h

Index: ui/aura/window_delegate.h
diff --git a/ui/aura/window_delegate.h b/ui/aura/window_delegate.h
index 4ba7ddcf60d8f89f881eba181056985de3abe35f..8dcc920b94faedadddd55ee702a9771108c39bfa 100644
--- a/ui/aura/window_delegate.h
+++ b/ui/aura/window_delegate.h
@@ -102,6 +102,9 @@ class AURA_EXPORT WindowDelegate : public ui::EventHandler {
   // above returns true.
   virtual void GetHitTestMask(gfx::Path* mask) const = 0;
 
+  // Sent when the server requests the window to close.
+  virtual void OnRequestClose();
+
  protected:
   ~WindowDelegate() override {}
 };