Bug 971546 - [System2] Instantiable Screenshot
Bug 971577 - [System] Make visibility manager instantiable
Bug 961800 - Implement Child Window Factory

Conflicts:
	apps/system/js/app_transition_controller.js
	apps/system/js/app_window.js
	apps/system/js/app_window_manager.js
	apps/system/js/cards_view.js
	apps/system/style/window.css
Bug 971556 - [System2] Instantiable SourceView.
Bug 970028 - Nicer activity opener animation
Bug 974828 - [Settings][dsds] Outgoing data confirmation is wrong

- update test
- change the way about how we show confirm window
Merge pull request #17263 from gasolin/bubble-merge225

cherry-pick Bubble-tea