Prefix string16 with base:: in ui/.

ui/views/widget/tooltip_manager_aura.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_VIEWS_WIDGET_TOOLTIP_MANAGER_AURA_H_
 #define UI_VIEWS_WIDGET_TOOLTIP_MANAGER_AURA_H_
 
 #include "base/compiler_specific.h"
 #include "base/strings/string16.h"
 #include "ui/gfx/point.h"
@@ skipping 34 matching lines @@
  private:
   View* GetViewUnderPoint(const gfx::Point& point);
   void UpdateTooltipForTarget(View* target,
                               const gfx::Point& point,
                               aura::Window* root_window);
 
   // Returns the Window the tooltip text is installed on.
   aura::Window* GetWindow();
 
   Widget* widget_;
-  string16 tooltip_text_;
+  base::string16 tooltip_text_;
 
   DISALLOW_COPY_AND_ASSIGN(TooltipManagerAura);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_TOOLTIP_MANAGER_AURA_H_