message: ref(hashmap): reference this.data to optimize for bundle size
diff: @@ -685,9 +685,10 @@ class MapPolyfill<T, KEY extends string | number = string | number> implements M
  // This is a potential performance bottleneck, see details in
  // https://github.com/ecomfe/zrender/issues/965, however it is now
  // less likely to occur as we default to native maps when possible.
  - for (const key in this.data) {
  - if (this.data.hasOwnProperty(key)) {
  - callback(this.data[key], key);
  + const data = this.data;
  + for (const key in data) {
  + if (data.hasOwnProperty(key)) {
  + callback(data[key], key);
  }
  }
  }
  