src/vs/editor/browser/view/viewController.ts/ViewController/_hasMulticursorModifier
class ViewController:	private _hasMulticursorModifier(data: IMouseDispatchData): boolean {
		switch (this.configuration.options.get(EditorOption.multiCursorModifier)) {
			case 'altKey':
				return data.altKey;
			case 'ctrlKey':
				return data.ctrlKey;
			case 'metaKey':
				return data.metaKey;
			default:
				return false;
		}
	}