Touchable Chrome: Fix profile avatar layout

- Adjust the alignment of the avatar icon in Touchable Chrome
  to follow the specs.
- Draw a circular 1px stroke around the avatar with the same
  color as that of the tab separator stroke.
- Refactor and gather some common code.

BUG=805267

Change-Id: I2be3181232cd43724f71b899de7905869b003360
Reviewed-on: https://chromium-review.googlesource.com/956809


Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542183}