Use physical pixels for display root ServerWindow.

services/ui/ws/display.h

Index: services/ui/ws/display.h
diff --git a/services/ui/ws/display.h b/services/ui/ws/display.h
index c5c74c005f12d3cfa8888fbec81415f5ef55c7c8..ca99bfb68ca7051fa8e67ef13923709026bdc8ba 100644
--- a/services/ui/ws/display.h
+++ b/services/ui/ws/display.h
@@ -163,8 +163,8 @@ class Display : public PlatformDisplayDelegate,
   void CreateWindowManagerDisplayRootFromFactory(
       WindowManagerWindowTreeFactory* factory);
 
-  // Creates the root ServerWindow for this display. The root window will have
-  // |size| in DIP.
+  // Creates the root ServerWindow for this display, where |size| is in physical
+  // pixels.
   void CreateRootWindow(const gfx::Size& size);
 
   // PlatformDisplayDelegate: