src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/isGroupMaximized
class EditorPart:	private isGroupMaximized(targetGroup: IEditorGroupView): boolean {
		for (const group of this.groups) {
			if (group === targetGroup) {
				continue; // ignore target group
			}

			if (!group.isMinimized) {
				return false; // target cannot be maximized if one group is not minimized
			}
		}

		return true;
	}