Completing refactor of startup_browser_creator_impl. This includes:

Completing refactor of startup_browser_creator_impl. This includes:

- Reintroducing session restore logic.

- Preventing Win 10 from branching on this codepath, as Win10 has been descoped from this launch.

- Correcting several small but critical bugs surfaced by session restore path:
  - Unexpected content in Guest Mode.
  - NTP showing unexpectedly on restored sessions.
  - Pinned tabs appearing duplicated on restored sessions.

BUG=660210
Review-Url: https://codereview.chromium.org/2457653003
Cr-Commit-Position: refs/heads/master@{#429303}
(cherry picked from commit 43f9c50bcb8b440c0f462b69f13b4bf9994e639b)

[Moe, 2016-11-11 23:23:20]

Committed patchset #1 (id:1) to pending queue manually as
24dcead8ebfce8fa89bec45c2e737725e9b340b3.