Update //base to chromium 9659b08ea5a34f889dc4166217f438095ddc10d2

base/i18n/case_conversion.h

 // Copyright (c) 2011 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 BASE_I18N_CASE_CONVERSION_H_
 #define BASE_I18N_CASE_CONVERSION_H_
 
 #include "base/i18n/base_i18n_export.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_piece.h"
 
 namespace base {
 namespace i18n {
 
-// Returns the lower case equivalent of string. Uses ICU's default locale.
-BASE_I18N_EXPORT string16 ToLower(const StringPiece16& string);
+// UNICODE CASE-HANDLING ADVICE
+//
+// In English it's always safe to convert to upper-case or lower-case text
+// and get a good answer. But some languages have rules specific to those
+// locales. One example is the Turkish I:
+//   http://www.i18nguy.com/unicode/turkish-i18n.html
+//
+// ToLower/ToUpper use the current ICU locale which will take into account
+// the user language preference. Use this when dealing with user typing.
+//
+// FoldCase canonicalizes to a standardized form independent of the current
+// locale. Use this when comparing general Unicode strings that don't
+// necessarily belong in the user's current locale (like commands, protocol
+// names, other strings from the web) for case-insensitive equality.
+//
+// Note that case conversions will change the length of the string in some
+// not-uncommon cases. Never assume that the output is the same length as
+// the input.
 
-// Returns the upper case equivalent of string. Uses ICU's default locale.
-BASE_I18N_EXPORT string16 ToUpper(const StringPiece16& string);
+// Returns the lower case equivalent of string. Uses ICU's current locale.
+BASE_I18N_EXPORT string16 ToLower(StringPiece16 string);
+
+// Returns the upper case equivalent of string. Uses ICU's current locale.
+BASE_I18N_EXPORT string16 ToUpper(StringPiece16 string);
+
+// Convert the given string to a canonical case, independent of the current
+// locale. For ASCII the canonical form is lower case.
+// See http://unicode.org/faq/casemap_charprop.html#2
+BASE_I18N_EXPORT string16 FoldCase(StringPiece16 string);
 
 }  // namespace i18n
 }  // namespace base
 
 #endif  // BASE_I18N_CASE_CONVERSION_H_