Split mode incognito extension can get misleading pref changed events from regular mode

chrome/test/data/extensions/api_test/preference/onchange/test.js

 // Copyright (c) 2012 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.
 
 // Content settings API test
 // Run with browser_tests --gtest_filter=ExtensionApiTest.PreferenceOnChange
 
 // Listen until |event| has fired with all of the values in |expected|.
 function listenUntil(event, expected) {
   var done = chrome.test.listenForever(event, function(value) {
     for (var i = 0; i < expected.length; i++) {
       if (chrome.test.checkDeepEq(expected[i], value)) {
         expected.splice(i, 1);
         if (expected.length == 0)
           done();
         return;
       }
     }
     chrome.test.fail("Unexpected event: " + JSON.stringify(value));
   });
 }
 
+// Fail if |event| is fired with |expected|. Because listenUntil stops listening
+// when |event| has fired with all the values in |expected|, it may not capture
+// superfluous unexpected events.
+function listenAndFailWhen(event, expected) {
+  return chrome.test.listenForever(event, function(value) {
+    if (chrome.test.checkDeepEq(expected, value))
+      chrome.test.fail("Unexpected event: " + JSON.stringify(value));
+  });
+}
+
 var pw = chrome.privacy.websites;
 chrome.test.runTests([
   function changeDefault() {
     // Changing the regular settings when no incognito-specific settings are
     // defined should fire two events.
     listenUntil(pw.thirdPartyCookiesAllowed.onChange, [{
       'value': false,
       'levelOfControl': 'controlled_by_this_extension'
     },
     {
       'value': false,
       'incognitoSpecific': false,
       'levelOfControl': 'controlled_by_this_extension'
     }]);
     pw.thirdPartyCookiesAllowed.set({
-      'value':false
+      'value': false
     }, chrome.test.callbackPass());
   },
   function changeIncognitoOnly() {
     listenUntil(pw.thirdPartyCookiesAllowed.onChange, [{
       'value': true,
       'incognitoSpecific': true,
       'levelOfControl': 'controlled_by_this_extension'
     }]);
+    var done = listenAndFailWhen(pw.thirdPartyCookiesAllowed.onChange, {
+      'value': true,
+      'levelOfControl': 'controlled_by_this_extension'
+    });
     pw.thirdPartyCookiesAllowed.set({

[Bernhard Bauer, 2012/06/20 18:55:36]

The problem is that pw.thirdPartyCookiesAllowed.set() is an asynchronous method,
so you can't call done() immediately afterwards. Instead, you can pass it in as
the callback instead of chrome.test.callbackPass(). I think that should take
care of the race condition (as we control all the timing now).

       'value': true,
       'scope': 'incognito_persistent'
     }, chrome.test.callbackPass());
+    done();
   },
   function changeDefaultOnly() {
     listenUntil(pw.thirdPartyCookiesAllowed.onChange, [{
       'value': true,
       'levelOfControl': 'controlled_by_this_extension'
     }]);
+    var done = listenAndFailWhen(pw.thirdPartyCookiesAllowed.onChange, {
+      'value': true,
+      'incognitoSpecific': true,
+      'levelOfControl': 'controlled_by_this_extension'
+    });
     pw.thirdPartyCookiesAllowed.set({
       'value': true
     }, chrome.test.callbackPass());
+    done();
   },
   function changeIncognitoOnlyBack() {
     // Change the incognito setting back to false so that we get an event when
     // clearing the value.
     listenUntil(pw.thirdPartyCookiesAllowed.onChange, [{
       'value': false,
       'incognitoSpecific': true,
       'levelOfControl': 'controlled_by_this_extension'
     }]);
     pw.thirdPartyCookiesAllowed.set({
@@ skipping 17 matching lines @@
       'levelOfControl': 'controllable_by_this_extension'
     },
     {
       'value': true,
       'incognitoSpecific': false,
       'levelOfControl': 'controllable_by_this_extension'
     }]);
     pw.thirdPartyCookiesAllowed.clear({}, chrome.test.callbackPass());
   }
 ]);