Add a bubble that lets the user know that one or more extensions have been
disabled because it/they didn't come from the webstore.

Also removing a few stray remnants of the Sideload Wipeout initiative, which are
no longer needed.

This is a retry of landing
https://codereview.chromium.org/70253002
... with only an if-check in the controller different (service_ can be null during testing).

BUG=318120
TBR=kalman

Review URL: https://codereview.chromium.org/77913005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236238 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236238