Revert 240031 "Rebuild the cache when a notification is marked a..."

> Rebuild the cache when a notification is marked as shown or displayed.
> 
> These operations update the unread count.
> 
> BUG=327055
> R=dewittj@chromium.org
> TEST=none
> 
> Review URL: https://codereview.chromium.org/98853010

TBR=mukai@chromium.org

Review URL: https://codereview.chromium.org/105733014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240045 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240045