Implement console.countReset() from the WHATWG Console Standard

R=bmeurer@chromium.org, dgozman@chromium.org, kozyatinskiy@chromium.org

Bug: chromium:839947
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I8a900e9cdf3e5b08506f709cf6497476c8c6c00b
Reviewed-on: https://chromium-review.googlesource.com/1044902Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Dominic Farolino <domfarolino@gmail.com>
Cr-Commit-Position: refs/heads/master@{#53106}