Remove unneeded bool from RenderView::selectionBounds
    
The boolean was added in r21387 and the added test
(fast/overflow/scroll-nested-positioned-layer-in-overflow.html)
is still passing. AFAICT the only adverse potential for this removal
is to invalidate more (as we don't apply the ancestors' clips)
    
The only meaningful test change is
fast/repaint/text-selection-rect-in-overflow-2.html
which had bad invalidations anyway (halfway through the selection)
so I don't think it's meaningful.

Review URL: https://codereview.chromium.org/570763003

git-svn-id: svn://svn.chromium.org/blink/trunk@182197 bbb929c8-8fbe-4397-9dbb-9b2b20218538