GitLab

If we close a tab, the tab index order can change, so, in
Navigate(), use the index before closing the other tab.

Bug: 780835
Change-Id: Ie88ab8e50528ec41e1048b3b5d12137f235202e3
Reviewed-on: https://chromium-review.googlesource.com/948822
Commit-Queue: Kevin Bailey <krb@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540987}