GitLab

 * AppListViewDelegate was accessing deleted search_provider.
 * DeviceSocketListener::StopListening can happen after DeviceSocketManager is deleted
 * Explicitly delete FilePathWatcher. This was causing
   recursive callback to FilePathWatcherImpl::Cancel from
   FilePathWatcherImpl::CancelOnMessageLoopThread, which
   caused crash.


Clean ups
 * change OnIO to OnFILE as they run on FILE thread.
 * removed unused singleton related code.

BUG=None
TEST=Run athena_main on desktop and close window.

Review URL: https://codereview.chromium.org/490033003

Cr-Commit-Position: refs/heads/master@{#291214}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291214 0039d316-1c4b-4281-b951-d872f2087c98