hi-dpi: convert _NET_WORKAREA from pixels.

Just like the gfx::Display member |bounds_| is not stored in pixels, we need to
convert |work_area_| from pixels.

Both are used in MenuController::UpdateInitialLocation (|work_area_| is
preferred over |bounds_|), which gets events with already converted
coordinates.

BUG=469373,143619

Review URL: https://codereview.chromium.org/1036263003

Cr-Commit-Position: refs/heads/master@{#322724}
1 file changed