Revert of Change default code flag to NewAvatarMenu. (patchset #29 id:580001 of https...

Revert of Change default code flag to NewAvatarMenu. (patchset #29 id:580001 of https://codereview.chromium.org/845373002/)

Reason for revert:
Broke Linux Valgrind tests on the waterfall. I'll need to do more testing / work on this CL before it's ready to land.

http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%285%29/builds/34330

Original issue's description:
> Change default code flag to NewAvatarMenu. Flags or Finch Configs still take priority, but all else being equal we should direct the user to NewAvatarMenu.
>
> This CL fixes a few issues that arise when the flag's on:
> - Missing alt text on chrome://settings
> - Unit tests for old components (OldAvatarMenu) need to force that state
> - The ProfileAvatarDownloader works automatically with NewAvatarMenu on - this needs to be accounted for so it doesn't leave images hanging around.
> - BookmarkBubbleSigninDelegate now triggers the User Menu, not a Sign in tab, on Desktop. (note this can't be easily tested in Cocoa)
>
> BUG=287883
>
> Committed: https://crrev.com/e4d285b050ab3429f7d937fde6234fcba07a360e
> Cr-Commit-Position: refs/heads/master@{#321770}

TBR=rogerta@chromium.org,shess@chromium.org,dbeam@chromium.org,noms@chromium.org,sky@chromium.org,mukai@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=287883

Review URL: https://codereview.chromium.org/1020863007

Cr-Commit-Position: refs/heads/master@{#321789}