[Cocoa] Add load delegate method for didChangeBackForwardList
https://bugs.webkit.org/show_bug.cgi?id=123136

Reviewed by Anders Carlsson.

* UIProcess/API/mac/WKBrowsingContextController.mm:
(didChangeBackForwardList): Added. Calls new delegate method.
(setUpPageLoaderClient):  Hook up new client function.
* UIProcess/API/mac/WKBrowsingContextLoadDelegate.h: Declare new delegate method.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157776 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Try to make the 32-bit Mac build happy.

* UIProcess/API/mac/WKBrowsingContextController.mm:
(setUpPageLoaderClient):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157777 268f45cc-cd09-0410-ab3c-d52691b4dbfc