Add more delegate callback methods to WKWebProcessPlugInLoadDelegate.

Patch by Yongjun Zhang <yongjun_zhang@apple.com> on 2014-01-17
Reviewed by Sam Weinig.

Add more WKWebProcessPlugInLoadDelegate callback methods so that a injected
bundle can listen/react to more frame loading events.

* WebProcess/InjectedBundle/API/Cocoa/WKWebProcessPlugInLoadDelegate.h: Add more delegate callback methods for
    WKWebProcessPlugInLoadDelegate.
* WebProcess/InjectedBundle/API/mac/WKWebProcessPlugInBrowserContextController.mm:
(didCommitLoadForFrame):
(didFinishDocumentLoadForFrame):
(didFailLoadWithErrorForFrame):
(didSameDocumentNavigationForFrame):
(didLayoutForFrame):
(setUpPageLoaderClient):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162203 268f45cc-cd09-0410-ab3c-d52691b4dbfc