This CL enables vr feature policy. So that, if you want to disable vr within
your application, you can delivering the following HTTP response header:
Feature-Policy: vr 'none'
If you want to enable vr for all frames(including cross-origin iframes),
delivering this:
Feature-Policy: vr *
If you want to enable vr just for your own origin, delivering this:
Feature-Policy: vr 'self'

To request vr for iframes, you can
<iframe src="https://foo.bar" allow="vr"></iframe> to grant vr to this iframe.

Bug: 666767
Change-Id: I48d7accf8553d6a9ac19d9f41dbbce2ff9934579
Reviewed-on: https://chromium-review.googlesource.com/636663
Reviewed-by: Ian Vollick <[email protected]>
Reviewed-by: Michael Thiessen <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Reviewed-by: Brandon Jones <[email protected]>
Reviewed-by: Ian Clelland <[email protected]>
Commit-Queue: Biao She <[email protected]>
Cr-Commit-Position: refs/heads/master@{#498674}