GitLab

Set up bidirectional communication between WebUI page and the backing
browser and set up a "hello world" example.

Bug: 1111229

Change-Id: I8a8ad38a02952a13a69723f33f5fbaa2fdf195d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353970
Commit-Queue: Sergei Datsenko <dats@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799054}