Make sure we clear registerProtocolHandler settings on page navigation.

BUG=298198

Review URL: https://codereview.chromium.org/25084003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226360 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226360