Move UTF16ToASCII, remove WideToASCII.

base/strings/utf_string_conversions.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_STRINGS_UTF_STRING_CONVERSIONS_H_
 #define BASE_STRINGS_UTF_STRING_CONVERSIONS_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 26 matching lines @@
 BASE_EXPORT string16 UTF8ToUTF16(const StringPiece& utf8);
 BASE_EXPORT bool UTF16ToUTF8(const char16* src, size_t src_len,
                              std::string* output);
 BASE_EXPORT std::string UTF16ToUTF8(const string16& utf16);
 
 // These convert an ASCII string, typically a hardcoded constant, to a
 // UTF16/Wide string.
 BASE_EXPORT std::wstring ASCIIToWide(const StringPiece& ascii);
 BASE_EXPORT string16 ASCIIToUTF16(const StringPiece& ascii);
 
+// Converts to 7-bit ASCII by truncating. The result must be known to be ASCII
+// beforehand.
+BASE_EXPORT std::string UTF16ToASCII(const string16& utf16);
+
 }  // namespace base
 
 // We are trying to get rid of wstring as much as possible, but it's too big a
 // mess to do it all at once.  These synonyms should be used when we really
 // should just be passing a string16 around, but we haven't finished porting
 // whatever module uses wstring and the conversion is being used as a stopgap.
 // This makes it easy to grep for the ones that should be removed.
 #define WideToUTF16Hack WideToUTF16
 #define UTF16ToWideHack UTF16ToWide
 
 #endif  // BASE_STRINGS_UTF_STRING_CONVERSIONS_H_