Chrome Version: 70.0.3501.0

What steps will reproduce the problem?
(1) Visit a page with links to other sites (e.g. news.ycombinator.com)
(2) Use devtools to throttle the network to make the following steps easier
(3) Click a link to start a cross-site navigation
(4) After the navigation commits, but before the old document stops being shown, cancel the load of the new page

What is the expected result?
The old document stops being shown after some timeout.

What happens instead?
The old document is shown indefinitely.

The |new_content_rendering_timeout_| is never started, so we never stop showing the old document.
We early return here before starting the timer:
https://cs.chromium.org/chromium/src/content/browser/renderer_host/render_widget_host_impl.cc?rcl=1e4639d7ac2bc1fdd25427f4df7239906d5c918d&l=1205