Continuation of CL 5685007, rename the singleton accessor method in more files.

app/active_window_watcher_x.h

Index: app/active_window_watcher_x.h
diff --git a/app/active_window_watcher_x.h b/app/active_window_watcher_x.h
index e54ee3c2de03665940127c3cdf78151836f4a876..4a89686e64eff9f0c0c98ece48610bb3837680f0 100644
--- a/app/active_window_watcher_x.h
+++ b/app/active_window_watcher_x.h
@@ -26,6 +26,8 @@ class ActiveWindowWatcherX {
     virtual ~Observer() {}
   };
 
+  static ActiveWindowWatcherX* GetInstance();
+
   static void AddObserver(Observer* observer);
   static void RemoveObserver(Observer* observer);
 
@@ -35,8 +37,6 @@ class ActiveWindowWatcherX {
   ActiveWindowWatcherX();
   ~ActiveWindowWatcherX();
 
-  static ActiveWindowWatcherX* GetInstance();
-
   void Init();
 
   // Sends a notification out through the NotificationService that the active