Add ol.geom.MultiPolygon#getArea

src/ol/geom/multipolygon.exports

@@ -1,4 +1,5 @@
 @exportSymbol ol.geom.MultiPolygon
+@exportProperty ol.geom.MultiPolygon.prototype.getArea
 @exportProperty ol.geom.MultiPolygon.prototype.getCoordinates
 @exportProperty ol.geom.MultiPolygon.prototype.getPolygons
 @exportProperty ol.geom.MultiPolygon.prototype.getType

src/ol/geom/multipolygon.js

@@ -49,6 +49,15 @@ ol.geom.MultiPolygon.prototype.containsXY = function(x, y) {
 };
 
 
+/**
+ * @return {number} Area.
+ */
+ol.geom.MultiPolygon.prototype.getArea = function() {
+  return ol.geom.flat.linearRingssArea(
+      this.flatCoordinates, 0, this.endss_, this.stride);
+};
+
+
 /**
  * @return {ol.geom.RawMultiPolygon} Coordinates.
  */