Switch ExternalProtocolObserver to use WebContentsUserData.

BUG=107201
TEST=no visible change


Review URL: https://chromiumcodereview.appspot.com/10961053

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@158878 0039d316-1c4b-4281-b951-d872f2087c98
4 files changed