Adding enums for Extension Toolbar histograms.

Histograms have already been committed (see https://codereview.chromium.org/141003006).

BUG=None
R=asvitkine@chromium.org

Review URL: https://codereview.chromium.org/133373005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248993 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248993
Refresh shortcuts when Drive status changes.

This patch reloads shortcuts if (1) drive becomes enabled/disabled, or (2) if its status changes.

TEST=Tested manually, hopefully all scenarios.
BUG=333090

Review URL: https://codereview.chromium.org/150203003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248994 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248994