Get rid of NavigationScheduler::LocationChangePending()

It exists to cope with the fact that NavigationScheduler doesn't
cancel parsing synchronously, but webpages implicitly expect
scheduling a navigation to stop processing of the existing document
in most cases.

Bug: 914587
Change-Id: I9cfaf2424d8d63198ad2f03b2e71123b0ed29bdd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1516395
Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643488}
17 files changed