Remove Widget::beforeMouseDown and Widget::afterMouseDown

Remove Widget::beforeMouseDown and Widget::afterMouseDown
https://bugs.webkit.org/show_bug.cgi?id=68570

Reviewed by Darin Adler.

These two member functions were originally added to avoid crashes due to removing NSViews while they were
being tracked by AppKit. Since they were added, we've moved away from NSViews for form controls, and the bugs in
AppKit that lead to crashes have been fixed.

This patch was rolled out in r95743 because it broke a bunch of tests. The patch accidentally removed setting back
m_sendingEventToSubview to false.

* page/mac/EventHandlerMac.mm:
(WebCore::EventHandler::passMouseDownEventToWidget):
* platform/Widget.h:
* platform/mac/WidgetMac.mm:
(WebCore::Widget::Widget):
(WebCore::Widget::removeFromSuperview):

* rendering/RenderWidget.cpp:
Change widgetHierarchyUpdateSuspendCount to be an unsigned integer instead of a size_t.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95749 268f45cc-cd09-0410-ab3c-d52691b4dbfc