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This is needed to get the touch hud application running out-of-process.
GetWindowBoundsInScreen was returning root-window coordinates, not
screen coordinates.

Bug: 840380
Test: added to views_mus_unittest
Change-Id: I1364d17a6eb87a748e50c5367dcf9164c25b5274
Reviewed-on: https://chromium-review.googlesource.com/1058320Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558752}