Remove Scrollbar dependency on Frame, FrameView and EventHandler
Remove Scrollbar dependency on Frame, FrameView and EventHandler

There is no need to set m_mousePressed from Scrollbar::mouseUp as
EventHandler::handleMouseReleaseEvent did that before calling mouseUp.
The other two callers of mouseUp involve scrollbars that are not in FrameViews.

BUG=297477

Review URL: https://codereview.chromium.org/61603003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@161628 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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