ui/aura: Use base::string16 now that string16 was moved into base namespace.

ui/aura/client/tooltip_client.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_AURA_CLIENT_TOOLTIP_CLIENT_H_
 #define UI_AURA_CLIENT_TOOLTIP_CLIENT_H_
 
 #include "ui/aura/aura_export.h"
 #include "ui/gfx/font.h"
 
 namespace aura {
 class RootWindow;
 class Window;
+
 namespace client {
 
 class AURA_EXPORT TooltipClient {
  public:
   // Informs the shell tooltip manager of change in tooltip for window |target|.
   virtual void UpdateTooltip(Window* target) = 0;
 
   // Sets the time after which the tooltip is hidden for Window |target|. If
   // |timeout_in_ms| is <= 0, the tooltip is shown indefinitely.
   virtual void SetTooltipShownTimeout(Window* target, int timeout_in_ms) = 0;
 
   // Enables/Disables tooltips.
   virtual void SetTooltipsEnabled(bool enable) = 0;
 };
 
 AURA_EXPORT void SetTooltipClient(RootWindow* root_window,
                                   TooltipClient* client);
 AURA_EXPORT TooltipClient* GetTooltipClient(RootWindow* root_window);
-AURA_EXPORT void SetTooltipText(Window* window, string16* tooltip_text);
-AURA_EXPORT const string16 GetTooltipText(Window* window);
+
+AURA_EXPORT void SetTooltipText(Window* window, base::string16* tooltip_text);
+AURA_EXPORT const base::string16 GetTooltipText(Window* window);
 
 }  // namespace client
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_TOOLTIP_CLIENT_H_