Update protobuf to r428, part 1.

third_party/protobuf/python/google/protobuf/internal/decoder.py

 # Protocol Buffers - Google's data interchange format
 # Copyright 2008 Google Inc.  All rights reserved.
 # http://code.google.com/p/protobuf/
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 558 matching lines @@
 
   type_id_tag_bytes = encoder.TagBytes(2, wire_format.WIRETYPE_VARINT)
   message_tag_bytes = encoder.TagBytes(3, wire_format.WIRETYPE_LENGTH_DELIMITED)
   item_end_tag_bytes = encoder.TagBytes(1, wire_format.WIRETYPE_END_GROUP)
 
   local_ReadTag = ReadTag
   local_DecodeVarint = _DecodeVarint
   local_SkipField = SkipField
 
   def DecodeItem(buffer, pos, end, message, field_dict):
+    message_set_item_start = pos
     type_id = -1
     message_start = -1
     message_end = -1
 
     # Technically, type_id and message can appear in any order, so we need
     # a little loop here.
     while 1:
       (tag_bytes, pos) = local_ReadTag(buffer, pos)
       if tag_bytes == type_id_tag_bytes:
         (type_id, pos) = local_DecodeVarint(buffer, pos)
@@ skipping 18 matching lines @@
     extension = extensions_by_number.get(type_id)
     if extension is not None:
       value = field_dict.get(extension)
       if value is None:
         value = field_dict.setdefault(
             extension, extension.message_type._concrete_class())
       if value._InternalParse(buffer, message_start,message_end) != message_end:
         # The only reason _InternalParse would return early is if it encountered
         # an end-group tag.
         raise _DecodeError('Unexpected end-group tag.')
+    else:
+      if not message._unknown_fields:
+        message._unknown_fields = []
+      message._unknown_fields.append((MESSAGE_SET_ITEM_TAG,
+                                      buffer[message_set_item_start:pos]))
 
     return pos
 
   return DecodeItem
 
 # --------------------------------------------------------------------
 # Optimization is not as heavy here because calls to SkipField() are rare,
 # except for handling end-group tags.
 
 def _SkipVarint(buffer, pos, end):
@@ skipping 78 matching lines @@
         tag (in which case the calling loop should break).
     """
 
     # The wire type is always in the first byte since varints are little-endian.
     wire_type = local_ord(tag_bytes[0]) & wiretype_mask
     return WIRETYPE_TO_SKIPPER[wire_type](buffer, pos, end)
 
   return SkipField
 
 SkipField = _FieldSkipper()