change the type property

modules/chart/ChartLayer.js

     super(id)
     this._option = option
     this._delegate = DomUtil.create('div', 'dc-chart')
-    this._setWrapperStyle()
     this._chart = undefined
-    this.type = Layer.getLayerType('chart')
+    this._setWrapperStyle()
     this._state = State.INITIALIZED
   }
 
+  get type() {
+    return Layer.getLayerType('chart')
+  }
+
   get chart() {
     return this._chart
   }