GitLab

Screenshots: https://drive.google.com/open?id=0B1B1Up4p2NRMRXpYbGJ6emtlX0U&authuser=1

TL; DR:
- never show a drop down arrow in the button.
- this means that we no longer need to do the auth error drawing magic, as we can use the
button's image. Also cleaned up ALL of that insane code.
- if there is one local, non-signed in profile, show a tiny button with a generic avatar
- in all other cases, show the avatar button with the profile name
- increased the button height by 1px so that it's perfectly aligned with the new tab button

BUG=410946

Review URL: https://codereview.chromium.org/605803002

Cr-Commit-Position: refs/heads/master@{#297255}