[DevTools] Typed events and event listeners.

third_party/WebKit/Source/devtools/front_end/ui/DropDownMenu.js

Index: third_party/WebKit/Source/devtools/front_end/ui/DropDownMenu.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/DropDownMenu.js b/third_party/WebKit/Source/devtools/front_end/ui/DropDownMenu.js
index 9ee2469e8601c1b175b72bf0f47124dc95cc8f26..f93e17e00a418f5c0096af4cfc1a84cb7c8aa095 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/DropDownMenu.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/DropDownMenu.js
@@ -4,7 +4,7 @@
 /**
  * @unrestricted
  */
-UI.DropDownMenu = class extends Common.Object {
+UI.DropDownMenu = class extends Common.ObjectBase {
   /**
    * @param {!Element} element
    */
@@ -32,7 +32,7 @@ UI.DropDownMenu = class extends Common.Object {
    * @param {string} id
    */
   _itemHandler(id) {
-    this.dispatchEventToListeners(UI.DropDownMenu.Events.ItemSelected, id);
+    this.dispatchEventToListeners(new UI.DropDownMenu.ItemSelectedEvent(id));
   }
 
   /**
@@ -59,7 +59,11 @@ UI.DropDownMenu = class extends Common.Object {
 /** @typedef {{id: string, title: string}} */
 UI.DropDownMenu.Item;
 
-/** @enum {symbol} */
-UI.DropDownMenu.Events = {
-  ItemSelected: Symbol('ItemSelected')
+UI.DropDownMenu.ItemSelectedEvent = class {
+  /**
+   * @param {string} id
+   */
+  constructor(id) {
+    this.id = id;
+  }
 };