GitLab

Introduces build flags to build the new IDL callback function
and IDL callback interface bindings.

Bug: 839389
Change-Id: I8714d28f1948bdee37cbde0c327f1ad57d406d41
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2418499Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810095}