GitLab

Adds a button to close tab and plumbing to send the close request to
Java.

Bug: 838937
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr
Change-Id: I45d6d8c3c66674bc472a17335a6e02195f8a23b8
Reviewed-on: https://chromium-review.googlesource.com/1050794
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557964}