 document.getElementById("baseline").getBoundingClientRect();
      let mspace = document.getElementById(aId).getBoundingClientRect();
      return {
          width: mspace.width,
          height: mspace.height,
          line_ascent: (baseline.top + baseline.bottom)/2 - mspace.top
      };
  }

  function runTests() {
      test(function() {
          let metrics = getMetrics("widthAttributePlusWidthProperty");
          assert_approx_equals(metrics.width, 200, epsilon,
                               "ms