Compute the popup location/size correctly when use-zoom-for-dsf is enabled.

third_party/WebKit/public/web/WebWidgetClient.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 157 matching lines @@
     // with the tap.
     // This provides a heuristic to help identify when a page is doing
     // something as a result of a tap without explicitly consuming the event.
     virtual void showUnhandledTapUIIfNeeded(const WebPoint& tappedPosition,
         const WebNode& tappedNode, bool pageChanged) { }
 
     // Called immediately after a mousedown event is dispatched due to a mouse
     // press or gesture tap.
     // Note: This is called even when the mouse down event is prevent default.
     virtual void onMouseDown(const WebNode& mouseDownNode) { }
+
+    // Converts the |rect| from Blink's Viewport coordinates to the
+    // coordinates in the native window used to display the content, in
+    // DIP.  They're identical in tradional world, but will differ when
+    // use-zoom-for-dsf feature is eanbled, and Viewport coordinates
+    // becomes DSF times larger than window coordinates.
+    // TODO(oshima): Update this comment when all platforms are migrated.
+    virtual void convertViewportToWindow(WebRect* rect) {}
+
 protected:
     ~WebWidgetClient() { }
 };
 
 } // namespace blink
 
 #endif