Revert 236000 "Add a bubble that lets the user know that one or ..."

> 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.
> 
> BUG=318120
> R=kalman@chromium.org, sky@chromium.org
> 
> Review URL: https://codereview.chromium.org/70253002

TBR=finnur@chromium.org

Review URL: https://codereview.chromium.org/59183003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236013 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236013