Fix bug with invalid chrome.sessions.onChanged listener.

chrome/test/data/extensions/api_test/sessions/onchanged/onchanged.js

+// Copyright 2016 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.
+
+function listener() {
+}
+
+// 0. After start, add and remove onChanged listener.
+// 1. Create incognito window.
+// 2. Remove the initial window.
+// 3. Create new window.
+// 4. Remove incognito window.
+// 5. Register listener and check it works.
+chrome.test.runTests([
+  function onChangedTest() {
+    chrome.sessions.onChanged.addListener(listener);
+    chrome.sessions.onChanged.removeListener(listener);
+    chrome.windows.getCurrent(function(win) {
+      first_win = win;
+      chrome.windows.create({incognito:true}, function(win) {
+        incognito_win = win;
+        chrome.windows.remove(first_win.id, function() {
+          chrome.windows.create({url:chrome.extension.getURL("../a.html")},
+                                function(win) {
+            new_win = win;
+            chrome.windows.remove(incognito_win.id, function() {
+              callbackCount = 0;
+              chrome.test.listenForever(chrome.sessions.onChanged, function() {
+                callbackCount++;
+              });
+              chrome.tabs.remove(new_win.tabs[0].id, function() {
+                chrome.test.assertTrue(callbackCount > 0);
+                chrome.test.succeed();
+              });
+            });
+          });
+        });
+      });
+    });
+  }
+]);