Ignore ibus preferences that get set at an indeterminate time

client/site_tests/desktopui_IBusTest/desktopui_IBusTest.py

Index: client/site_tests/desktopui_IBusTest/desktopui_IBusTest.py
diff --git a/client/site_tests/desktopui_IBusTest/desktopui_IBusTest.py b/client/site_tests/desktopui_IBusTest/desktopui_IBusTest.py
index c825ded3fd3dcd89dd3bae1bff69bcfde3cda9b6..975594540b770b380adfe33e89142a53b2d8a675 100644
--- a/client/site_tests/desktopui_IBusTest/desktopui_IBusTest.py
+++ b/client/site_tests/desktopui_IBusTest/desktopui_IBusTest.py
@@ -171,14 +171,6 @@ class desktopui_IBusTest(site_ui_test.UITest):
                                   'engine/PinyinLookupTableOrientation',
                                   'engine/PinyinSpecialPhrases',
 
-                                  # These preferences are actually read, but
-                                  # ibus-daemon reads them before chrome
-                                  # connects,  so they show up as a false
-                                  # failure.
-                                  'general/hotkeynext_engine_in_menu',
-                                  'general/hotkeyprevious_engine',
-                                  'generalglobal_engine',
-
                                   # We don't set these prefernces.
                                   'general/hotkeytrigger',
                                   'generalembed_preedit_text',
@@ -187,6 +179,13 @@ class desktopui_IBusTest(site_ui_test.UITest):
                                   'generaluse_global_engine',
                                   'generaluse_system_keyboard_layout'])
 
+        # These preferences are actually written, but due to a race condition
+        # on startup, they can be read by ibus-daemon before chrome connects,
+        # and so sometimes they show up as a false failure.
+        ignored_unwritten = set(['general/hotkeynext_engine_in_menu',
+                                 'general/hotkeyprevious_engine',
+                                 'generalglobal_engine'])
+
         self.preload_engines(engine_list)
 
         # ibus takes some time to preload the engines, and they can't be
@@ -209,6 +208,9 @@ class desktopui_IBusTest(site_ui_test.UITest):
         actual_unread = set(re.split('\n', match.group(1).strip()))
         actual_unwritten = set(re.split('\n', match.group(2).strip()))
 
+        # Filter out any preferences we're ignoring
+        actual_unwritten.difference_update(ignored_unwritten)
+
         new_unread = actual_unread.difference(expected_unread)
         now_read = expected_unread.difference(actual_unread)
         new_unwritten = actual_unwritten.difference(expected_unwritten)