src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/getGroups
class EditorPart:	getGroups(order = GroupsOrder.CREATION_TIME): IEditorGroupView[] {
		switch (order) {
			case GroupsOrder.CREATION_TIME:
				return this.groups;

			case GroupsOrder.MOST_RECENTLY_ACTIVE: {
				const mostRecentActive = coalesce(this.mostRecentActiveGroups.map(groupId => this.getGroup(groupId)));

				// there can be groups that got never active, even though they exist. in this case
				// make sure to just append them at the end so that all groups are returned properly
				return distinct([...mostRecentActive, ...this.groups]);
			}
			case GroupsOrder.GRID_APPEARANCE: {
				const views: IEditorGroupView[] = [];
				if (this.gridWidget) {
					this.fillGridNodes(views, this.gridWidget.getViews());
				}

				return views;
			}
		}
	}