Update the remaining include paths of base/string_piece.h to its new location.

ui/webui/web_ui_util.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_WEBUI_WEB_UI_UTIL_H_
 #define UI_WEBUI_WEB_UI_UTIL_H_
 
 #include <string>
 
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "base/values.h"
 #include "ui/base/layout.h"
+#include "ui/base/ui_export.h"
 #include "ui/base/window_open_disposition.h"
-#include "ui/base/ui_export.h"
 
 class GURL;
 class SkBitmap;
 
 namespace webui {
 
 // Convenience routine to convert SkBitmap object to data url
 // so that it can be used in WebUI.
 UI_EXPORT std::string GetBitmapDataUrl(const SkBitmap& bitmap);
 
@@ skipping 25 matching lines @@
                                  ui::ScaleFactor* scale_factor);
 
 // Helper function to set the font family, size, and text direction into the
 // given dictionary.
 UI_EXPORT void SetFontAndTextDirection(
     base::DictionaryValue* localized_strings);
 
 }  // namespace webui
 
 #endif  // UI_WEBUI_WEB_UI_UTIL_H_