Move latin1_string_conversions to base

webkit/glue/latin1_string_conversions.cc

-// Copyright 2013 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.
-
-#include "webkit/glue/latin1_string_conversions.h"
-
-namespace webkit_glue {
-
-string16 Latin1OrUTF16ToUTF16(size_t length,
-                              const Latin1Char* latin1,
-                              const char16* utf16) {
-  if (!length)
-    return string16();
-  if (latin1)
-    return string16(latin1, latin1 + length);
-  return string16(utf16, utf16 + length);
-}
-
-}  // namespace webkit_glue