Use FeaturePolicy to implement iframe[allowfullscreen]

Use FeaturePolicy to implement iframe[allowfullscreen]

The previous CL (https://crrev.com/719a425c) tried to handle this in fullscreenIsSupported(), which misses the important case where the Feature Policy API is enabled, but the site uses 'allowfullscreen' iframe attributes.

This CL roughly mimics the intended behaviour of feature-policy allowfullscreen, by allowing access to fullscreen in same-origin iframes, and in cross-origin iframes where either a Feature-Policy header or an 'allowfullscreen' attribute is used, and the parent frame allows fullscreen.

BUG=666761
Review-Url: https://codereview.chromium.org/2585363002
Cr-Commit-Position: refs/heads/master@{#446393}
(cherry picked from commit 39d97d6645829da8b4c402b3112c81ebbe53004d)

Review-Url: https://codereview.chromium.org/2662443004 .
Cr-Commit-Position: refs/branch-heads/2987@{#152}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/6a505c5e0e74b61d0ab2e194abd3533150f1131f

[iclelland, 2017-01-27 19:46:16]

Description was changed from

==========
Use FeaturePolicy to implement iframe[allowfullscreen]

The previous CL (https://crrev.com/719a425c) tried to handle this in
fullscreenIsSupported(), which misses the important case where the Feature
Policy API is enabled, but the site uses 'allowfullscreen' iframe attributes.

This CL roughly mimics the intended behaviour of feature-policy allowfullscreen,
by allowing access to fullscreen in same-origin iframes, and in cross-origin
iframes where either a Feature-Policy header or an 'allowfullscreen' attribute
is used, and the parent frame allows fullscreen.

BUG=666761

Review-Url: https://codereview.chromium.org/2585363002
Cr-Commit-Position: refs/heads/master@{#446393}
(cherry picked from commit 39d97d6645829da8b4c402b3112c81ebbe53004d)
==========

to

==========
Use FeaturePolicy to implement iframe[allowfullscreen]

The previous CL (https://crrev.com/719a425c) tried to handle this in
fullscreenIsSupported(), which misses the important case where the Feature
Policy API is enabled, but the site uses 'allowfullscreen' iframe attributes.

This CL roughly mimics the intended behaviour of feature-policy allowfullscreen,
by allowing access to fullscreen in same-origin iframes, and in cross-origin
iframes where either a Feature-Policy header or an 'allowfullscreen' attribute
is used, and the parent frame allows fullscreen.

BUG=666761

Review-Url: https://codereview.chromium.org/2585363002
Cr-Commit-Position: refs/heads/master@{#446393}
(cherry picked from commit 39d97d6645829da8b4c402b3112c81ebbe53004d)

Review-Url: https://codereview.chromium.org/2662443004 .
Cr-Commit-Position: refs/branch-heads/2987@{#152}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/6a505c5e0e74b61d0ab2e194abd3...
==========

[iclelland, 2017-01-27 19:46:17]

Committed patchset #1 (id:1) manually as
6a505c5e0e74b61d0ab2e194abd3533150f1131f.