Keep browser process alive while there are platform apps with background pages running.

chrome/test/data/extensions/api_test/media_galleries_private/attachdetach/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.
 
 var attachedDeviceId = '42';
 
 var testAttach = function(details) {
   // Save the device id for the detach test.
   attachedDeviceId = details.deviceId;
   // The C++ test code will check if this is ok.
@@ skipping 30 matching lines @@
   chrome.mediaGalleriesPrivate.onDeviceDetached.addListener(testDummyDetach);
   chrome.test.sendMessage('add_dummy_detach_ok');
 }
 
 function removeAttachListener() {
   chrome.mediaGalleriesPrivate.onDeviceAttached.removeListener(testAttach);
   chrome.test.sendMessage('remove_attach_ok');
 }
 
 function removeDummyDetachListener() {
-  chrome.mediaGalleriesPrivate.onDeviceAttached.removeListener(testDummyDetach);
+  chrome.mediaGalleriesPrivate.onDeviceDetached.removeListener(testDummyDetach);
   chrome.test.sendMessage('remove_dummy_detach_ok');
 }