NavigatorRegisterProtocolHandler can call ChromeClient directly, not need to call ChromeClient through Chrome. Adam Barth suggested this way at the comment of other bug, https://bugs.webkit.org/show_bug.cgi?id=73176#c21.
Created attachment 140857 [details] Patch
Comment on attachment 140857 [details] Patch Thanks.
Thanks for the review!
Comment on attachment 140857 [details] Patch Clearing flags on attachment: 140857 Committed r116497: <http://trac.webkit.org/changeset/116497>
All reviewed patches have been landed. Closing bug.