Introduce ui.dll / libui.so for the component build.

ui/base/x/active_window_watcher_x.h

 // Copyright (c) 2011 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.
 
 #ifndef UI_BASE_X_ACTIVE_WINDOW_WATCHER_X_H_
 #define UI_BASE_X_ACTIVE_WINDOW_WATCHER_X_H_
 #pragma once
 
 #include <gdk/gdk.h>
 
 #include "base/basictypes.h"
 #include "base/memory/singleton.h"
 #include "base/observer_list.h"
 #include "ui/base/gtk/gtk_signal.h"
+#include "ui/ui_api.h"
 
 namespace ui {
 
 // This is a helper class that is used to keep track of which window the X
 // window manager thinks is active. Add an Observer to listener for changes to
 // the active window.
-class ActiveWindowWatcherX {
+class UI_API ActiveWindowWatcherX {
  public:
   class Observer {
    public:
     // |active_window| will be NULL if the active window isn't one of Chrome's.
     virtual void ActiveWindowChanged(GdkWindow* active_window) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
@@ skipping 23 matching lines @@
                      OnWindowXEvent, GdkXEvent*, GdkEvent*);
 
   ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ActiveWindowWatcherX);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_X_ACTIVE_WINDOW_WATCHER_X_H_