Revert "Have NavigationSimulator support browser-initiated navigations"

This reverts commit e97788658c0b72fa47612c1c70803abf3a7d4ad7.

Reason for revert: This breaks Linux CFI unit_tests: https://uberchromegw.corp.google.com/i/chromium.memory/builders/Linux%20CFI/builds/904

Original change's description:
> Have NavigationSimulator support browser-initiated navigations
> 
> This CL adds support for simulating browser-initiated navigations using
> NavigationSimulator. It removes the one usage outside of content/ of
> RenderFrameHostTester::SimulateNavigationStart in simulation of
> browser-initiated navigations. It also makes
> TestWebContents::NavigateAndCommit use NavigationSimulator.
> 
> BUG=728571
> 
> Cq-Include-Trybots: master.tryserver.chromium.linux:linux_site_isolation
> Change-Id: Ib295868db2a3aab5828a178aba7b92d77ed9b2ba
> Reviewed-on: https://chromium-review.googlesource.com/583096
> Commit-Queue: Camille Lamy <clamy@chromium.org>
> Reviewed-by: Matt Menke <mmenke@chromium.org>
> Reviewed-by: Nasko Oskov <nasko@chromium.org>
> Reviewed-by: Timothy Loh <timloh@chromium.org>
> Reviewed-by: Nathan Parker <nparker@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#493442}

TBR=nasko@chromium.org,felt@chromium.org,timloh@chromium.org,clamy@chromium.org,mmenke@chromium.org,nparker@chromium.org

Change-Id: I672aad0aabb65e5633e10750515fba12b88617aa
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 728571
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_site_isolation
Reviewed-on: https://chromium-review.googlesource.com/610940
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#493475}
8 files changed