Prefix string16 with base:: in ui/.

ui/views/corewm/tooltip.h

 // Copyright 2013 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_COREWM_TOOLTIP_H_
 #define UI_VIEWS_COREWM_TOOLTIP_H_
 
 #include "base/strings/string16.h"
 #include "ui/views/views_export.h"
 
 namespace aura {
 class Window;
 }
 
 namespace gfx {
 class Point;
 }
 
 namespace views {
 namespace corewm {
 
 // Tooltip is responsible for showing the tooltip in an appropriate manner.
 // Tooltip is used by TooltipController.
 class VIEWS_EXPORT Tooltip {
  public:
   virtual ~Tooltip() {}
 
   // Updates the text on the tooltip and resizes to fit.
   virtual void SetText(aura::Window* window,
-                       const string16& tooltip_text,
+                       const base::string16& tooltip_text,
                        const gfx::Point& location) = 0;
 
   // Shows the tooltip at the specified location (in screen coordinates).
   virtual void Show() = 0;
 
   // Hides the tooltip.
   virtual void Hide() = 0;
 
   // Is the tooltip visibile?
   virtual bool IsVisible() = 0;
 };
 
 }  // namespace corewm
 }  // namespace views
 
 #endif  // UI_VIEWS_COREWM_TOOLTIP_H_