Load last committed item after session restoration is complete.

Additionally fixed extra WebStateObserver::TitleWasSet calls.

This makes session restoration behavior similar for both legacy
and slim navigation managers.

Bug: 877671
Change-Id: I2c0265914ed1a6738335efd031f752db9c0a295f
Reviewed-on: https://chromium-review.googlesource.com/c/1347316
Reviewed-by: Danyao Wang <danyao@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610935}
3 files changed