GitLab

This CL handles two cases:
1) When restore_session.html is first loaded, set virtual URL to the
   item that will be displayed when session is fully restored.
2) If a restore_session.html is loaded in the webview, set the virtual
   URL to the encoded URL, as that will be the page that will eventually
   be displayed.

Moved session restore logic into a separate util file so it's easier to
test.

Bug: 789993
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I1547f792f1e3de0bf97d11dced09383b82c507fc
Reviewed-on: https://chromium-review.googlesource.com/817713
Commit-Queue: Danyao Wang <danyao@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524418}