Pull in ASCII<->UTF16 from Chromium

base/strings/string_util.h

 // Copyright 2006-2008 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 MINI_CHROMIUM_BASE_STRINGS_STRING_UTIL_H_
 #define MINI_CHROMIUM_BASE_STRINGS_STRING_UTIL_H_
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
+#include "base/strings/string_piece.h"
 
 namespace base {
 
 int vsnprintf(char* buffer, size_t size, const char* format, va_list arguments)
     PRINTF_FORMAT(3, 0);
 
+bool IsStringASCII(const StringPiece& str);
+bool IsStringASCII(const StringPiece16& str);
+
 }  // namespace base
 
 #if defined(OS_WIN)
 #include "base/strings/string_util_win.h"
 #elif defined(OS_POSIX)
 #include "base/strings/string_util_posix.h"
 #endif
 
 template <class string_type>
 inline typename string_type::value_type* WriteInto(string_type* str,
                                                    size_t length_with_null) {
   DCHECK_NE(0u, length_with_null);
   str->reserve(length_with_null);
   str->resize(length_with_null - 1);
 
   if (length_with_null <= 1)
     return NULL;
 
   return &((*str)[0]);
 }
 
 #endif  // MINI_CHROMIUM_BASE_STRINGS_STRING_UTIL_H_