Enable DCHECK for renderer-initiated navigations requiring initiator.

This CL enables a DCHECK to enforce that all renderer-initiated
navigations supply an initiator origin. It is an invariant that should
always hold, so this DCHECK will help enforce it at least in our test
suites.

It changes the various cases covered by tests today where initiator
origin is not supplied.

Change-Id: I5298e352d1b75e7ec1fb673aa9d8383beb0584d4
Reviewed-on: https://chromium-review.googlesource.com/c/1385495
Commit-Queue: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621626}
10 files changed