GitLab

This change:
1) Adds focus rings to the tab-close button
2) Moves the new tab button to last in the TabStrip's focus order if it is not
   in LEADING position so that the keyboard focus order within the TabStrip is
   correct

Positioning the ring for the tab-close button requires some finesse: the tab
close button has its margins adjusted, but the focus ring only needs to draw
around the visible part of the button.

Bug: 848299
Change-Id: I226683d3a8829f5a88e9bf102b4c8ba4ecfae459
Reviewed-on: https://chromium-review.googlesource.com/1091131Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565673}