Resize the new avatar menu button correctly when the profile name changes.
Bonus: elide long names.

Screenshot of fix: https://drive.google.com/a/chromium.org/file/d/0B1B1Up4p2NRMbkNWYkpQY1RIb1E/edit?usp=sharing

BUG=311010
TEST=With the --new-profile-management flag, start a browser. Change the
active profile name to something really long. The button should resize
and the text should get elided. Now change it to something really short.
The button should resize correctly again.

Review URL: https://codereview.chromium.org/50213005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232387 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232387