Reset onlyNeededPositionedMovementLayout in RenderObject::clearRepaintState()

Previously there seems nowhere resetting the flag.

Review URL: https://codereview.chromium.org/267863003

git-svn-id: svn://svn.chromium.org/blink/trunk@173354 bbb929c8-8fbe-4397-9dbb-9b2b20218538