WPTs for pre-navigation check of form-submission should be added

[mbrodesser-Igalia]

See e.g. https://jsfiddle.net/fhrpo2zj/2/.

The spec covers this, since "type" in [1] may be "form-submission" and [2] is fully exercised for that type.

CC @lukewarlow, @otherdaniel

[1] https://w3c.github.io/webappsec-csp/#should-block-navigation-request [2] https://w3c.github.io/trusted-types/dist/spec/#require-trusted-types-for-pre-navigation-check

[ghost]

Adding test is WIP at https://bugzilla.mozilla.org/show_bug.cgi?id=1921008.

[koto]

The test seems to be added already, the finals bit in https://github.com/web-platform-tests/wpt/commit/4db7dc692be3aca644252623d69d5db5113541f7. @mbrodesser-Igalia, can this be closed now?