Disallow syncing of extensions with third-party update URLs or plugins.

BUG=49346,46516
TEST=new unit tests, manual

Review URL: http://codereview.chromium.org/2884025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53102 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed