[ Feature Policy ] Followup on Opener Policies

This CL fixes a few types and mistakes in the original CL which
implemented opener policies (CL: 1384992).

Besides, this CL adds two WPTs to complement the test coverage for
"FeaturePolicyForSandbox". The current tests verify correctness of
propagation in the following cases:

  1- "window.open" from an <iframe> that is not sandbox.
  2- "window.open" from an <iframe> that is sandboxed but allows
  escaping.

In case (1) the policies are expected to be inherited but in case (2)
they should not be inherited from the <iframe>.

Future tests add support for cross-origin frames/window as well as
rel=noopener case if need be.

TBR=mkwst@chromium.org

Bug: 774620, 926293
Change-Id: I2da875a008584c7e2015a020fcad92e9528e748d
Reviewed-on: https://chromium-review.googlesource.com/c/1483942
Commit-Queue: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Reviewed-by: Ɓukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635680}
19 files changed