Bug 971515 - [System2] Instantiable MediaRecording
Bug 971577 - [System] Make visibility manager instantiable
Merge pull request #16588 from huchengtw-moz/system/Bug_971515_instantiable_media_recording

Bug 971515 - [System2] Instantiable MediaRecording, r=alive
Merge pull request #16591 from rexboy7/system-bug971577-bubbletea

Bug 971577 - [System] Make visibility manager instantiable. r=alive
Bug 961800 - Implement Child Window Factory
Merge pull request #16556 from alivedise/bugzilla/961800_master/child-window-factory

Bug 961800 - Child Window Factory, r=etienne.
Bug 971512 - [System] Instantiable layout manager