Code cleanup, calculate clientX/clientY in one central place.

        * dom/EventTargetNode.h:
        * dom/EventTargetNode.cpp: (WebCore::EventTargetNode::dispatchMouseEvent):
        Renamed parameters to pageX/Y since they aren't clientX/Y values.
        Removed code to compute clientX/Y (was a bit confused in naming before),
        because that's now done inside MouseEvent.

        * dom/MouseEvent.h:
        * dom/MouseEvent.cpp:
        (WebCore::MouseEvent::MouseEvent): Removed clientX/Y parameters.
        (WebCore::MouseEvent::initMouseEvent): Added comments about problems I noticed.
        (WebCore::MouseEvent::which): Fixed comment that confusingly mentioned KHTML,
        when it was talking about the DOM standard.

        * dom/MouseRelatedEvent.h:
        * dom/MouseRelatedEvent.cpp:
        (WebCore::contentsX): Added helper function.
        (WebCore::contentsY): Ditto.
        (WebCore::MouseRelatedEvent::MouseRelatedEvent): Removed clientX/Y parameter,
        and added code to compute clientX/Y based on pageX/Y.
        (WebCore::MouseRelatedEvent::receivedTarget): Fixed comments.

        * dom/WheelEvent.h:
        * dom/WheelEvent.cpp: (WebCore::WheelEvent::WheelEvent): Removed clientX/Y
        parameter.

        * page/FrameView.cpp: (WebCore::FrameView::dispatchDragEvent): Removed the code
        to compute coordinates, and renamed the confusingly named clientPos (which was
        a page-relative position) to contentsPos.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15047 268f45cc-cd09-0410-ab3c-d52691b4dbfc