flex-direction: column;
      display: flex;
    }
    toolbar {
      flex: 0 0 auto;
      border-bottom: 1px solid black;
      display: flex;
    }
    result-area {
      flex: 1 1 auto;
      display: block;
      min-height: 0;
      overflow-y: auto;
    }
    </style>

    <toolbar id="toolbar"></toolbar>
    <result-area id="result_area"></result-area>
  </template>