Mus: Fixes rendering of transparent containers.

services/ui/ws/frame_generator.h

Index: services/ui/ws/frame_generator.h
diff --git a/services/ui/ws/frame_generator.h b/services/ui/ws/frame_generator.h
index c23e3b7da545bb938499dd5e49fa1b371db65f31..1872f1a5ed546e43df98e049585d54bda30659eb 100644
--- a/services/ui/ws/frame_generator.h
+++ b/services/ui/ws/frame_generator.h
@@ -27,6 +27,10 @@ class SurfacesState;
 
 namespace ws {
 
+namespace test {
+class FrameGeneratorTest;
+}
+
 class FrameGeneratorDelegate;
 class ServerWindow;
 
@@ -48,6 +52,8 @@ class FrameGenerator {
   bool is_frame_pending() { return frame_pending_; }
 
  private:
+  friend class ui::ws::test::FrameGeneratorTest;
+
   void WantToDraw();
 
   // This method initiates a top level redraw of the display.