Prevents for h264 attaching SPS and PPS Nalu if already present on Windows
This patch prevents adding the SPS and PPS present in extradata WMFMediaDataEncoder,
if the data already contains SPS and PPS. Otherwise, the resulting Byte stream would
not be spec complained and be rejected by Chromium, for example.
It also includes a WPT test.
Differential Revision: https://phabricator.services.mozilla.com/D226985
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1927280
gecko-commit: 8588b5f0f391f973a081a9495182dc73135b388b
gecko-reviewers: chunmin