Revert "Merge pull request #16588 from huchengtw-moz/system/Bug_971515_instantiable_media_recording"

This reverts commit 37739cb918affe7080960a7525f6b7e0e81318bb, reversing
changes made to 84446d88705396651afc97ae626e62666f9e14de.

Conflicts:
	apps/system/js/media_recording.js
	apps/system/test/unit/bootstrap_test.js