message: Set attributes on the super class too.
diff: @@ -79,6 +79,10 @@ export function CustomElement(tag: string): (target: any) => any {
  super.removeAttribute(attrName);
  }
  }
  +
  + [decoratorData.superSetAttributeSymbol](attrName: string, value: any): void {
  + super.setAttribute(attrName, value);
  + }
  };
  decoratorData.validate();
  @@ -113,6 +117,8 @@ class DecoratorData {
  private _attrNameAttrDataMap = new Map<string, AttributeData>();
  // ^ Key is a kebab-case attribute name.
  + superSetAttributeSymbol = Symbol("SuperSetAttribute")
  +
  constructor(private _elementProto: any) {
  }
  @@ -160,8 +166,7 @@ class DecoratorData {
  attrData.instanceValueMap.set(this, newValue);
  if (decoratorData._isInstanceConstructed(this)) {
  - // FIXME
  - // this[SetParentAttributeSymbol].call(this, attrData.attributeName, newValue);
  + this[decoratorData.superSetAttributeSymbol].call(this, attrData.attributeName, newValue);
  }
  // Notify observers
  