Do not use overlays when VR shell is enabled.

ui/display/display.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_DISPLAY_DISPLAY_H_
 #define UI_DISPLAY_DISPLAY_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
@@ skipping 173 matching lines @@
     depth_per_component_ = depth_per_component;
   }
 
   // True if this is a monochrome display (e.g, for accessiblity). Used by media
   // query APIs.
   bool is_monochrome() const { return is_monochrome_; }
   void set_is_monochrome(bool is_monochrome) {
     is_monochrome_ = is_monochrome;
   }
 
+  // True if this is a virtual display (e.g, for vr).
+  bool in_vr() const { return true; }
+  void set_in_vr(bool in_vr) {
+    in_vr_ = in_vr;
+  }
+
+
  private:
   int64_t id_;
   gfx::Rect bounds_;
   gfx::Rect work_area_;
   float device_scale_factor_;
   Rotation rotation_;
   TouchSupport touch_support_;
   gfx::Size maximum_cursor_size_;
   gfx::ICCProfile icc_profile_;
   int color_depth_;
   int depth_per_component_;
   bool is_monochrome_;
+  bool in_vr_;
 
 #if !defined(OS_IOS)
   friend struct mojo::StructTraits<display::mojom::DisplayDataView,
                                    display::Display>;
 #endif
 };
 
 }  // namespace display
 
 #endif  // UI_DISPLAY_DISPLAY_H_