Revert of Convert Google Now's Authentication Manager to use Promises (https://codereview.chromium.org/162273002/)

Reason for revert:
Promise.catch may not always be called back, breaking an assumption about the task tracking system.

Original issue's description:
> Convert Google Now's Authentication Manager to use Promises
> 
> BUG=164227
> R=rgustafson@chromium.org, skare@chromium.org, vadimt@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=252109

TBR=skare@chromium.org,rgustafson@chromium.org,vadimt@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=164227

Review URL: https://codereview.chromium.org/171713007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252134 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252134