Linux Aura: If title buttons are on the left, show avatar on the right.

BUG=323068
TEST=Use incognito. In Ubuntu Unity, close/minimize/maximize should be
on the left, and avatar should be on the right.

Review URL: https://codereview.chromium.org/85353002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238012 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238012