kiosk: Use ExtensionUpdater for launch time update.

Previous r244632 took a shortcut and use uninstall/reinstall to update
the app. This is wrong and causes the app local data being lost. This
CL fixes the problem by using ExtensionUpdater.

BUG=345756
R=tengs@chromium.org

Review URL: https://codereview.chromium.org/177533006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253086 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253086
Add UMA stat to count unique origins using getUserMedia and RTCPeerConnection.

BUG=none

Review URL: https://codereview.chromium.org/174013003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253087 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253087