The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ba36721fd456323e90165becf0c439d04da6e53e

commit ba36721fd456323e90165becf0c439d04da6e53e
Author: Devlin Cronin <rdevlin.cronin@chromium.org>
Date: Fri Sep 22 03:35:49 2017

[Extensions Docs] Add documentation on Extension API Schemas

Add some basic documentation on extension API schemas.

Bug: 734198

Change-Id: I4a29787ff489929d5051ca06fca27bbe6dc7111c
Reviewed-on: https://chromium-review.googlesource.com/677130
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503622}
[add] https://crrev.com/ba36721fd456323e90165becf0c439d04da6e53e/chrome/common/extensions/api/schemas.md

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There's some documentation here now (from #1), but the constructs karandeepb@ mentioned in #0 are still undocumented.  Flipping to available.