Redesign of the avatar menu button.

Screenshots: https://drive.google.com/folderview?id=0B1B1Up4p2NRMYm8zRzFhQkpCTUE&usp=sharing
This is behind the --new-profile-management flag, and shows the avatar
switcher as a menu button in the caption area. The button shows the user's
name, rather than an image.

Caveats:
-- The resources needed by the buttons are in CL: <insert here>
-- Currently this works on Aero and themed windows. Haven't tested on Win8/Metro,
but I'm suspicious it does nothing.

BUG=287883

Review URL: https://codereview.chromium.org/24647003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228293 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228293