mus: Make sure window parenting happens in the window server.

services/ui/ws/platform_display_default.h

Index: services/ui/ws/platform_display_default.h
diff --git a/services/ui/ws/platform_display_default.h b/services/ui/ws/platform_display_default.h
index 12c07f26da1c0cd51e555f672e96637fd5a63570..ca1b7d59927a71db19a28ed6ec43734bea685baf 100644
--- a/services/ui/ws/platform_display_default.h
+++ b/services/ui/ws/platform_display_default.h
@@ -44,6 +44,7 @@ class PlatformDisplayDefault : public PlatformDisplay,
   gfx::Rect GetBounds() const override;
   bool UpdateViewportMetrics(const display::ViewportMetrics& metrics) override;
   const display::ViewportMetrics& GetViewportMetrics() const override;
+  gfx::AcceleratedWidget GetAcceleratedWidget() const override;
   FrameGenerator* GetFrameGenerator() override;
 
  private:
@@ -81,6 +82,7 @@ class PlatformDisplayDefault : public PlatformDisplay,
 
   display::ViewportMetrics metrics_;
   std::unique_ptr<ui::PlatformWindow> platform_window_;
+  gfx::AcceleratedWidget widget_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformDisplayDefault);
 };