Take 2 at browser_sync::ExtensionsActivityMonitor....

chrome/browser/sync/util/extensions_activity_monitor.h

Index: chrome/browser/sync/util/extensions_activity_monitor.h
===================================================================
--- chrome/browser/sync/util/extensions_activity_monitor.h	(revision 30162)
+++ chrome/browser/sync/util/extensions_activity_monitor.h	(working copy)
@@ -42,8 +42,8 @@
   typedef std::map<std::string, Record> Records;
 
   // Creates an ExtensionsActivityMonitor to monitor extensions activities on
-  // |ui_loop|.
-  explicit ExtensionsActivityMonitor(MessageLoop* ui_loop);
+  // ChromeThread::UI.
+  ExtensionsActivityMonitor();
   ~ExtensionsActivityMonitor();
 
   // Fills |buffer| with snapshot of current records in constant time by
@@ -62,13 +62,10 @@
   Records records_;
   mutable Lock records_lock_;
 
-  // Kept for convenience.
-  MessageLoop* const ui_loop_;
-
   // Used only from UI loop.
   NotificationRegistrar registrar_;
 };
 
 }  // namespace browser_sync
 
-#endif  // CHROME_BROWSER_SYNC_UTIL_EXTENSIONS_ACTIVITY_MONITOR_H_
+#endif  // CHROME_BROWSER_SYNC_UTIL_EXTENSIONS_ACTIVITY_MONITOR_H_