src/vs/platform/keybinding/common/abstractKeybindingService.ts/KeybindingModifierSet/constructor
class KeybindingModifierSet:	constructor(source: ResolvedKeybindingPart | null) {
		this._ctrlKey = source ? source.ctrlKey : false;
		this._shiftKey = source ? source.shiftKey : false;
		this._altKey = source ? source.altKey : false;
		this._metaKey = source ? source.metaKey : false;
	}