Prevented false error messages from user manager UI.
Messages like "Pod offsetHeight (0) and POD_HEIGHT (226) are not equal." were
reported on desktop user manager. It happened because |placePods_| method call
were made, when account picker was hidden.
In addition deprecated |webkitRequestAnimationFrame| was replaced with
|requestAnimationFrame| in login code.
BUG=none
TEST=Run user manager, see that messages are gone.
Review URL: https://codereview.chromium.org/
422563002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287407 0039d316-1c4b-4281-b951-d872f2087c98