Remove a deprecated wstring ToLower function.

app/l10n_util.cc

Index: app/l10n_util.cc
diff --git a/app/l10n_util.cc b/app/l10n_util.cc
index 0837c0220bf61a60613c084777e4ce05356c918f..249d8cf491c7ad6f92dec50e6374c3b381647de7 100644
--- a/app/l10n_util.cc
+++ b/app/l10n_util.cc
@@ -720,12 +720,6 @@ std::wstring TruncateString(const std::wstring& string, size_t length) {
   return string.substr(0, index) + kElideString;
 }
 
-#if defined(WCHAR_T_IS_UTF32)
-std::wstring ToLower(const std::wstring& string) {
-  return UTF16ToWide(ToLower(WideToUTF16(string)));
-}
-#endif  // defined(WCHAR_T_IS_UTF32)
-
 string16 ToLower(const string16& string) {
   icu::UnicodeString lower_u_str(
       icu::UnicodeString(string.c_str()).toLower(icu::Locale::getDefault()));