RenderCounter::updateCounter should trigger a relayout.

      Currently, the method calls setTextInternal() - which updates the text
but doesn't mark the node for layout and pref widths recalc. This can
leave stale text boxes behind.

Instead, we should use setText() - which triggers the needed
invalidations.

BUG=444707
R=jbroman@chromium.org,eae@chromium.org

Review URL: https://codereview.chromium.org/842913002

git-svn-id: svn://svn.chromium.org/blink/trunk@188180 bbb929c8-8fbe-4397-9dbb-9b2b20218538