GitLab

The `tabs` custom bindings have been entirely replaced by native
counterparts. Remove the JS version.

Bug: 938998
Change-Id: I7a55e00fb2bf008bcecae6c3b00179040f6aba8a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1559255Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649257}