Bunch of match preview tweaks:

base/string_util.h

 // Copyright (c) 2010 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 working with strings.
 
 #ifndef BASE_STRING_UTIL_H_
 #define BASE_STRING_UTIL_H_
 #pragma once
 
@@ skipping 564 matching lines @@
 // number less one. Eg $$->$, $$$->$$, etc. The offsets parameter here can be
 // NULL. This only allows you to use up to nine replacements.
 string16 ReplaceStringPlaceholders(const string16& format_string,
                                    const std::vector<string16>& subst,
                                    std::vector<size_t>* offsets);
 
 std::string ReplaceStringPlaceholders(const base::StringPiece& format_string,
                                       const std::vector<std::string>& subst,
                                       std::vector<size_t>* offsets);
 
-// Single-string shortcut for ReplaceStringHolders.
+// Single-string shortcut for ReplaceStringHolders. |offset| may be NULL.
 string16 ReplaceStringPlaceholders(const string16& format_string,
                                    const string16& a,
                                    size_t* offset);
 
 // If the size of |input| is more than |max_len|, this function returns true and
 // |input| is shortened into |output| by removing chars in the middle (they are
 // replaced with up to 3 dots, as size permits).
 // Ex: ElideString(L"Hello", 10, &str) puts Hello in str and returns false.
 // ElideString(L"Hello my name is Tom", 10, &str) puts "Hell...Tom" in str and
 // returns true.
@@ skipping 29 matching lines @@
 #elif defined(WCHAR_T_IS_UTF32)
   typedef uint32 Unsigned;
 #endif
 };
 template<>
 struct ToUnsigned<short> {
   typedef unsigned short Unsigned;
 };
 
 #endif  // BASE_STRING_UTIL_H_