title: Get geometry(coord) with getSource or getLayer in mapbox gl
body: <p>I have 5 geojson layers - each layer have one line. I want to get the coordinates of the line with map.getSource or map.getLayer, but I don't see any geometry properites.
  I can get the coordinates with this:</p>
  
  <pre><code>var features = map.queryRenderedFeatures({layers:[layerName]});
  console.log(features[0].geometry); 
  </code></pre>
  
  <p>My geojson is:</p>
  
  <pre><code>var layer = map.addLayer({
          "id": layerName,
          "type": "line",
          "source": {
              "type": "geojson",
              "data": {
                  "type": "Feature",
                  "properties": {},
                  "geometry": {
                      "type": "LineString",
                      "coordinates": line
                  }
              }
          },
          "layout": {
              "line-join": "round",
              "line-cap": "round"
          },
          "paint": {
              "line-color": "red",
              "line-width": 13
          }
      });
  </code></pre>