Make Blink's unit tests closer to real world

... by replicating async navigation logic from RenderFrameImpl.

Some tests have to change to account for new asynchrony.

Bug: 855189
Change-Id: Ib92d8f4a9f6afc6527e9db7fc03765e0f6138e76
Reviewed-on: https://chromium-review.googlesource.com/c/1396399
Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620960}
10 files changed