Added checks to handle unsyncable extensions.

BUG=49346,46516
TEST=manual, unit tests

Review URL: http://codereview.chromium.org/2884027

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53127 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed