part 6) Add missing tests to <to-javascript-parent-initiated-child-csp.html>.
Those tests cover all injection sinks mentioned at [1]. There could be
other injection sinks accepting javascript: URLs but I'm not aware of
such.
Tests for when the parent and child differ and both have a CSP will be
added in a separate patch.
[1] https://developer.mozilla.org/en-US/docs/Web/URI/Schemes/javascript#description
Differential Revision: https://phabricator.services.mozilla.com/D227508
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1567058
gecko-commit: c8ab9251d2334f8abfd5c710b9cbe8d773067223
gecko-reviewers: freddyb