GitLab

Instead of exposing internal methods to layout test through
TestRunner, we can just emulate user navigating away from the page.

Bug: 855189
Change-Id: I4cd08357e7929108ad7c9fe79f7f5eeec13e7888
Reviewed-on: https://chromium-review.googlesource.com/c/1334192Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608536}