Do not use overlays when VR shell is enabled.

content/public/common/screen_info.h

Index: content/public/common/screen_info.h
diff --git a/content/public/common/screen_info.h b/content/public/common/screen_info.h
index b758fed561b4c0562967ab437ab7a3655ebe1f3f..db887dac454396a161f793d903e9c1a8a1df3239 100644
--- a/content/public/common/screen_info.h
+++ b/content/public/common/screen_info.h
@@ -36,6 +36,9 @@ struct CONTENT_EXPORT ScreenInfo {
     // This can be true for black and white printers
     bool is_monochrome = false;
 
+    // This is true when display is a virtual display.
+    bool is_virtual = false;
+
     // The display monitor rectangle in virtual-screen coordinates. Note that
     // this may be negative.
     gfx::Rect rect;