Reland of FrameGenerator should not be created until an AcceleratedWidget is available

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 ca1b7d59927a71db19a28ed6ec43734bea685baf..54d36d8b5e860bd2c47674e1a2b075a7af056472 100644
--- a/services/ui/ws/platform_display_default.h
+++ b/services/ui/ws/platform_display_default.h
@@ -26,7 +26,7 @@
 // FrameGenerator for Chrome OS.
 class PlatformDisplayDefault : public PlatformDisplay,
                                public ui::PlatformWindowDelegate,
-                               private FrameGeneratorDelegate {
+                               public FrameGeneratorDelegate {
  public:
   explicit PlatformDisplayDefault(const PlatformDisplayInitParams& init_params);
   ~PlatformDisplayDefault() override;
@@ -83,6 +83,8 @@
   display::ViewportMetrics metrics_;
   std::unique_ptr<ui::PlatformWindow> platform_window_;
   gfx::AcceleratedWidget widget_;
+  ServerWindow* root_window_;
+  float init_device_scale_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformDisplayDefault);
 };