Don't crash when HTMLPopoverAttribute is manually disabled

The MediaControlPopupMenuElement was converted [1] to use the
Popover API after HTMLPopoverAttribute was shipped by default [2].
However, there are {D}CHECKs that make sure popover features
are only used when the feature is enabled. This means that on
systems with the HTMLPopoverAttribute feature manually disabled,
these CHECKs will get hit. For now, at least don't crash. The
popover will still not function. But this is a short term patch
until the Popover feature flag is removed completely on August
8, 2023.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/4204913
[2] https://chromium-review.googlesource.com/c/chromium/src/+/4206587

Fixed: 1466192
Change-Id: Ibbd7a66b678df35bd183a00971611a9d45e6fa9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4704788
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Auto-Submit: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1173318}