Remove repaint during layout when updating scrollbars.

This CL fixes up the various places where we invalidate and immediately paint
the scrollbars. (RenderLayerScrollableArea, RenderListBox and FrameView).

This necessitates storing the scrollbar damage information in the scrollable
area and then checking/painting if needed in repaintTree().

BUG=336253

Review URL: https://codereview.chromium.org/148093006

git-svn-id: svn://svn.chromium.org/blink/trunk@166235 bbb929c8-8fbe-4397-9dbb-9b2b20218538