message: refactor(build/emitter): simplify isCovariantEventHandler()
diff: @@ -579,10 +579,8 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor, iterator: boo
  // Here we know the property is already defined on the interface, we elide its declaration if the parent has the same handler defined
  function isCovariantEventHandler(i: Browser.Interface, p: Browser.Property) {
  return isEventHandler(p) &&
  - iNameToEhParents[i.name] && iNameToEhParents[i.name].length > 0 &&
  iNameToEhParents[i.name].some(
  - i => iNameToEhList[i.name] && iNameToEhList[i.name].length > 0 &&
  - iNameToEhList[i.name].some(e => e.name === p.name));
  + parent => parent.properties?.property.hasOwnProperty(p.name));
  }
  function emitProperty(prefix: string, i: Browser.Interface, emitScope: EmitScope, p: Browser.Property) {
  