Prefix string16 with base:: in ui/.

ui/views/test/child_modal_window.h

 // Copyright (c) 2012 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_VIEWS_TEST_CHILD_WMODAL_WINDOW_H_
 #define UI_VIEWS_TEST_CHILD_WMODAL_WINDOW_H_
 
 #include "ui/views/controls/button/button.h"
 #include "ui/views/widget/widget_delegate.h"
 #include "ui/views/widget/widget_observer.h"
@@ skipping 17 matching lines @@
 
   void ShowChild();
   gfx::NativeWindow GetModalParent() const;
   gfx::NativeWindow GetChild() const;
 
  private:
   Widget* CreateChild();
 
   // Overridden from WidgetDelegate:
   virtual View* GetContentsView() OVERRIDE;
-  virtual string16 GetWindowTitle() const OVERRIDE;
+  virtual base::string16 GetWindowTitle() const OVERRIDE;
   virtual bool CanResize() const OVERRIDE;
   virtual void DeleteDelegate() OVERRIDE;
   virtual void Layout() OVERRIDE;
   virtual void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) OVERRIDE;
 
   // Overridden from ButtonListener:
   virtual void ButtonPressed(Button* sender,
                              const ui::Event& event) OVERRIDE;
 
@@ skipping 17 matching lines @@
   // The child window.
   Widget* child_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildModalParent);
 };
 
 }  // namespace test
 }  // namespace views
 
 #endif  // UI_VIEWS_TEST_CHILD_WMODAL_WINDOW_H_