Sort extensions in chrome://extensions by (order, name, id) rather than just
(order, name) for the case when extensions have the same name. Fix a comment.

BUG=298960

Review URL: https://codereview.chromium.org/24766002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227416 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227416