Navigation: Adding StartWithParams to NavigationSimulatorImpl - 1/2

This patch implements the first content specific NavigationSimulator
usage, support for LoadURLWithParams. We provide a SetLoadURLParams,
that if provided, will be used when starting the navigation.

This new capability also allows us to remove all direct calls of
LoadURLParams to unit tests. The only remaining ones in
navigator_impl_unittest.cc that are quite more complex than these
will be handled in a followup of this patch, here:
https://chromium-review.googlesource.com/c/chromium/src/+/1409196


Bug: 728571
Change-Id: Iaada51795c3edb4e906f8ff6d819f1e417f8010a
Reviewed-on: https://chromium-review.googlesource.com/c/1404088
Commit-Queue: Arthur Hemery <ahemery@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622537}
6 files changed