Clean up feature policy flags.

This fixes the default feature list, ensuring that features only appear
in it if they are actually enabled with the correct runtime feature
flags. Even if they are shipped as 'stable', they can still be disabled,
and should not be parsed in that case, or appear in the output of
document.policy.allowedFeatures().

Bug: 862601
Change-Id: I207a17818ed6696e9d029b86adcf42e4b58b6516
Reviewed-on: https://chromium-review.googlesource.com/1133307
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574677}
2 files changed