https://bugs.webkit.org/show_bug.cgi?id=114941

Reviewed by Darin Adler.

It's a layering violation that Scrollbar uses EventHandler, Frame
and FrameView. Frame is used to get the EventHandler that is used
to set mousePressed to false after a Scrollbar::mouseUp(). This is
not really needed, since EventHandler already sets m_mousePressed
to false when calling Scrollbar::mouseUp(). The PopupMenu windows
implementation also calls Scrollbar::mouseUp(), but that scrollbar
is not inside a FrameView.

* platform/Scrollbar.cpp:
(WebCore::Scrollbar::isScrollViewScrollbar):
isScrollViewScrollbar() is a method of ScrollView so we don't need
to cast to FrameView.
(WebCore::Scrollbar::mouseUp): Remove EventHandler ussage.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148892 268f45cc-cd09-0410-ab3c-d52691b4dbfc