Updates the CTS test runner JS to split logs into multiple
pieces if they're in danger of running into the payload
size limit that the test harness has.
crrev.com/c/3584705 must land in Chromium first.
Bug: chromium:1315658
Change-Id: I30ff416741515ce784116a2cbfbf193b6a4d71f1
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/86509
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@google.com>