MacBooks allow for diagonal scrolling.  Also enhance the PlatformWheelEvent
        to allow for diagonal scrolling.

        Reviewed by Eric

        * dom/EventTargetNode.cpp:
        (WebCore::EventTargetNode::dispatchWheelEvent):
        * dom/WheelEvent.cpp:
        (WebCore::WheelEvent::WheelEvent):
        (WebCore::WheelEvent::initWheelEvent):
        * dom/WheelEvent.h:
        (WebCore::WheelEvent::wheelDelta):
        (WebCore::WheelEvent::wheelDeltaX):
        (WebCore::WheelEvent::wheelDeltaY):
        * dom/WheelEvent.idl:
        * page/FrameView.cpp:
        (WebCore::FrameView::handleWheelEvent):
        * platform/PlatformWheelEvent.h:
        (WebCore::PlatformWheelEvent::deltaX):
        (WebCore::PlatformWheelEvent::deltaY):
        (WebCore::PlatformWheelEvent::normalize):
        * platform/mac/WheelEventMac.mm:
        (WebCore::PlatformWheelEvent::PlatformWheelEvent):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@16467 268f45cc-cd09-0410-ab3c-d52691b4dbfc