Disentangle repaint-after-compositing from updateLayerPositionsAfterLayout

Rather than using updateLayerPositions to propagate mayNeedPaintInvalidation
down the tree, this CL adds the notion of forcing a check for paint
invalidation during the invalidate tree walk. Now, if a RenderBox or a
relatively positioned RenderInline moves, we'll check all its in-flow
descendants for whether they need their paint invalidated.

R=jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/433603004

git-svn-id: svn://svn.chromium.org/blink/trunk@179514 bbb929c8-8fbe-4397-9dbb-9b2b20218538