GitLab

Implements step 8.1. of
https://heycam.github.io/webidl/#create-an-interface-prototype-object

Bug: 811029
Change-Id: I0feb1c16cf12585db8847c82d4efa342701bebcb
Reviewed-on: https://chromium-review.googlesource.com/1098914
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567580}