Don't flag form submissions as client redirects for extensions use

We have two subtly different definitions of a client redirect. One
is exposed on the extensions webNavigation API, the other is used
in headless mode and is based on whether a navigation used to go
through NavigationScheduler. These definitions differ on whether
form submissions should be client redirects. Enable each use case to
see the definition it expects.

Bug: 960653
Test: WebNavigationApiTest.FormSubmission
Change-Id: If727762b7b5feef79e2e5059eddc75d57f982e08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628158
Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663349}
13 files changed