message: fix mapbox viz
diff: @@ -65,7 +65,7 @@ class ScatterPlotGlowOverlay extends React.Component {
  const canvas = this.refs.overlay;
  const ctx = canvas.getContext('2d');
  const radius = props.dotRadius;
  - const mercator = ViewportMercator(props);
  + const mercator = new ViewportMercator(props);
  const rgb = props.rgb;
  const clusterLabelMap = [];
  let maxLabel = -1;
  @@ -264,7 +264,7 @@ class MapboxViz extends React.Component {
  }
  render() {
  - const mercator = ViewportMercator({
  + const mercator = new ViewportMercator({
  width: this.props.sliceWidth,
  height: this.props.sliceHeight,
  longitude: this.state.viewport.longitude,
  