Adding gmail_compose_discard.json pageset

Review URL: https://chromiumcodereview.appspot.com/23480020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225217 0039d316-1c4b-4281-b951-d872f2087c98
New avatar menu UI fixes:
- added a "view all profiles" button that opens the user manager
- added a custom button that has a background when hovered
(see https://docs.google.com/file/d/0B1B1Up4p2NRMbktkLXQ0SFRxYXc/edit?usp=sharing)
- cleaned up all the incorrect usages of "vertical" when I actually meant "horizontal" (>_<)

(no-trying the CL because the linux_aura bot is broken)

BUG=287883
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/23526074

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225218 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225218