Add FakeChromeEvent

chrome/test/data/webui/fake_chrome_event.js

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview Fake implementations of ChromeEvent.
+ */
+
+/**
+ * @constructor
+ * @extends {ChromeEvent}
+ */
+function FakeChromeEvent() {
+  /** @type {!Set<!Function>} */
+  this.listeners_ = new Set();
+}
+
+FakeChromeEvent.prototype = {
+  /** @param {Function} listener */
+  addListener: function(listener) {
+    assertFalse(this.listeners_.has(listener));
+    this.listeners_.add(listener);
+  },
+
+  /** @param {Function} listener */
+  removeListener: function(listener) {
+    assertTrue(this.listeners_.has(listener));
+    this.listeners_.delete(listener);
+  },
+
+  /** @param {...} args */
+  callListeners: function(...var_args) {
+    this.listeners_.forEach(function(l) {
+      l.apply(null, var_args);
+    });
+  }
+};