message: Suppress pointless attribute updates in custom element decorators
diff: @@ -163,8 +163,12 @@ class DecoratorData {
  newValue = updatedValue;
  }
  - attrData.instanceValueMap.set(this, newValue);
  + const oldValue = attrData.instanceValueMap.get(this);
  + if (oldValue === newValue) {
  + return;
  + }
  + attrData.instanceValueMap.set(this, newValue);
  if (decoratorData._isInstanceConstructed(this)) {
  this[decoratorData.superSetAttributeSymbol].call(this, attrData.attributeName, newValue);
  }
  