[Template Expressions] changing ${ leader to $i18n{

ui/base/template_expressions.h

 // Copyright 2015 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.
 
 // This file defines utility functions for replacing template expressions.
 // For example "Hello ${name}" could have ${name} replaced by the user's name.
 
 #ifndef UI_BASE_TEMPLATE_EXPRESSIONS_H_
 #define UI_BASE_TEMPLATE_EXPRESSIONS_H_
 
 #include <map>
 #include <string>
 
 #include "base/strings/string_piece.h"
 #include "ui/base/ui_base_export.h"
 
 namespace ui {
 
+// Map of strings for template replacement in |ReplaceTemplateExpressions|.
+typedef std::map<const std::string, std::string> TemplateReplacements;
+
 // Replace ${foo} in the format string with the value for the foo key in
 // |subst|.  If the key is not found in the |substitutions| that item will
 // be unaltered.
 UI_BASE_EXPORT std::string ReplaceTemplateExpressions(
     base::StringPiece format_string,
-    const std::map<base::StringPiece, std::string>& substitutions);
+    const TemplateReplacements& substitutions);
 
 }  // namespace ui
 
 #endif  // UI_BASE_TEMPLATE_EXPRESSIONS_H_