https://bugs.webkit.org/show_bug.cgi?id=127085

Patch by Ian Henderson <ianh@apple.com> on 2014-01-16
Reviewed by Antti Koivisto.

Expose WKView's scroll view as a property.  In order to support
clients calling setDelegate:, we create a forwarder object that sends
delegate methods to both WKView (the "internal delegate") and the
publicly-exposed delegate (the "external delegate").

* UIProcess/API/Cocoa/WKView.h:
* UIProcess/API/ios/WKScrollView.h:
* UIProcess/API/ios/WKScrollView.mm:
(-[WKScrollViewDelegateForwarder initWithInternalDelegate:externalDelegate:]):
(-[WKScrollViewDelegateForwarder methodSignatureForSelector:]):
(-[WKScrollViewDelegateForwarder respondsToSelector:]):
(-[WKScrollViewDelegateForwarder forwardInvocation:]):
(-[WKScrollView setInternalDelegate:]):
(-[WKScrollView setDelegate:]):
(-[WKScrollView delegate]):
Pretend like _externalDelegate is the real delegate to avoid exposing
our internal delegate or forwarder object.
(-[WKScrollView _updateDelegate]):
(-[WKScrollView dealloc]):
* UIProcess/API/ios/WKViewIOS.mm:
(-[WKView scrollView]):
(-[WKView _commonInitializationWithContextRef:pageGroupRef:relatedToPage:]):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162121 268f45cc-cd09-0410-ab3c-d52691b4dbfc