Fix comment bug in I71a8d356e868dc7715b030ca1078da4ec39368c3.

This is a coment-only follow up CL for I71a8d356e868dc7715b030ca,
which wrongly changed coordinates from window-local to view-local
(relative to FloatingToolbar#mParent) when showing PopupWindow.

The position of PopupWindow still needs to be specified in
window-local coordinates as we had done before
I71a8d356e868dc7715b030ca1078da4ec39368c3.

Currently the problem might not be visible to users because
  1. FloatingToolbar is not a public API hence all the instances
     are under our controll.
  2. FloatingToolbar#mParent is alwasy initialized with
     PhoneWindow#getDecorView() for now.

Bug: 22335001
Change-Id: Ib641dda49f7ab1c7d60207c36a47767bb408971c