[Mac] Gesture scrolls don't work in the WebKit1 clients after scrolling a non-scrollable iFrame
https://bugs.webkit.org/show_bug.cgi?id=136029
<rdar://problem/17767169>

Reviewed by Maciej Stachowiak.

This is difficult to test in our layout tests, since it relies on specific host application
behavior.

If the platform widget is a frame view (IFrame), and we are in WebKit1, 'passWheelEventToWidget'
has already called 'scrollWheel' on the underlying platform widget. We need to return true in
this case to avoid getting multiple copies of the scrollWheel event sent to the platform widget.

* page/EventHandler.cpp:
(WebCore::EventHandler::platformCompletePlatformWidgetWheelEvent): Revise default stub to
accept a Widget* argument.
(WebCore::EventHandler::handleWheelEvent):
* page/EventHandler.h:
* page/mac/EventHandlerMac.mm:
(WebCore::EventHandler::platformCompletePlatformWidgetWheelEvent): Check for WK1 case and
return 'true' when the underlying NSScrollView has been issues a scrollWheel event.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@172703 268f45cc-cd09-0410-ab3c-d52691b4dbfc