Save and restore tab groups

This implements basic session restore functionality for tab
groups. Currently, only whole browser session restore is supported;
restoring a window or a tab from the history menu won't restore
groups.

Bug: 905491
Change-Id: Ib6ad643c7efd75f468bb518fa5881b17a3d9f05f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1627947
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666500}
22 files changed