Access singletons with a new GetInstance() method instead of Singleton<T>.

app/active_window_watcher_x.cc

 // Copyright (c) 2009 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.
 
 #include <X11/Xlib.h>
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
 
 #include "app/active_window_watcher_x.h"
 
 static Atom kNetActiveWindowAtom = None;
 
 // static
+ActiveWindowWatcherX* ActiveWindowWatcherX::GetInstance() {
+  return Singleton<ActiveWindowWatcherX>::get();
+}
+
+// static
 void ActiveWindowWatcherX::AddObserver(Observer* observer) {
-  Singleton<ActiveWindowWatcherX>::get()->observers_.AddObserver(observer);
+  ActiveWindowWatcherX::GetInstance()->observers_.AddObserver(observer);
 }
 
 // static
 void ActiveWindowWatcherX::RemoveObserver(Observer* observer) {
-  Singleton<ActiveWindowWatcherX>::get()->observers_.RemoveObserver(observer);
+  ActiveWindowWatcherX::GetInstance()->observers_.RemoveObserver(observer);
 }
 
 ActiveWindowWatcherX::ActiveWindowWatcherX() {
   Init();
 }
 
 ActiveWindowWatcherX::~ActiveWindowWatcherX() {
 }
 
 void ActiveWindowWatcherX::Init() {
@@ skipping 57 matching lines @@
       window_watcher);
   XEvent* xev = static_cast<XEvent*>(xevent);
 
   if (xev->xany.type == PropertyNotify &&
       xev->xproperty.atom == kNetActiveWindowAtom) {
     watcher->NotifyActiveWindowChanged();
   }
 
   return GDK_FILTER_CONTINUE;
 }