Do not use overlays when VR shell is enabled.

ui/display/display.h

Index: ui/display/display.h
diff --git a/ui/display/display.h b/ui/display/display.h
index 9980057e066c3dd2a1a31000480ec33d5b6c5bd9..50942a34288c81d4880e1b280edf0e0baa15c54e 100644
--- a/ui/display/display.h
+++ b/ui/display/display.h
@@ -190,6 +190,12 @@ class DISPLAY_EXPORT Display final {
     is_monochrome_ = is_monochrome;
   }
 
+  // True if this is a virtual display (e.g, for vr).
+  bool is_virtual() const { return is_virtual_; }
+  void set_is_virtual(bool is_virtual) {
+    is_virtual_ = is_virtual;
+  }
+
  private:
   int64_t id_;
   gfx::Rect bounds_;
@@ -202,6 +208,7 @@ class DISPLAY_EXPORT Display final {
   int color_depth_;
   int depth_per_component_;
   bool is_monochrome_ = false;
+  bool is_virtual_ = false;
 
 #if !defined(OS_IOS)
   friend struct mojo::StructTraits<display::mojom::DisplayDataView,