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

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

Index: chrome/test/data/extensions/api_test/preference/onchange/test.js
diff --git a/chrome/test/data/extensions/api_test/preference/onchange/test.js b/chrome/test/data/extensions/api_test/preference/onchange/test.js
index f67ec474733c43aa531d18abcb8b8e87973ec57e..9bf9ebd31c702524f355a50ce2588593aedbaa6b 100644
--- a/chrome/test/data/extensions/api_test/preference/onchange/test.js
+++ b/chrome/test/data/extensions/api_test/preference/onchange/test.js
@@ -20,6 +20,16 @@ function listenUntil(event, expected) {
   });
 }
 
+// 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() {
@@ -35,7 +45,7 @@ chrome.test.runTests([
       'levelOfControl': 'controlled_by_this_extension'
     }]);
     pw.thirdPartyCookiesAllowed.set({
-      'value':false
+      'value': false
     }, chrome.test.callbackPass());
   },
   function changeIncognitoOnly() {
@@ -44,19 +54,30 @@ chrome.test.runTests([
       '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