Update //third_party/protobuf to version 3.

third_party/protobuf/src/google/protobuf/unittest_mset_wire_format.proto

Index: third_party/protobuf/src/google/protobuf/unittest_mset_wire_format.proto
diff --git a/third_party/protobuf/src/google/protobuf/unittest_mset.proto b/third_party/protobuf/src/google/protobuf/unittest_mset_wire_format.proto
similarity index 77%
copy from third_party/protobuf/src/google/protobuf/unittest_mset.proto
copy to third_party/protobuf/src/google/protobuf/unittest_mset_wire_format.proto
index 3497f09fa6d41b7b38357e7f2610dfb5c087d3e4..04e4352e06d3ee03482dcaca97a27c78efa6bea4 100644
--- a/third_party/protobuf/src/google/protobuf/unittest_mset.proto
+++ b/third_party/protobuf/src/google/protobuf/unittest_mset_wire_format.proto
@@ -1,6 +1,6 @@
 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
-// http://code.google.com/p/protobuf/
+// https://developers.google.com/protocol-buffers/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
@@ -34,9 +34,12 @@
 //
 // This file contains messages for testing message_set_wire_format.
 
-package protobuf_unittest;
+syntax = "proto2";
+package proto2_wireformat_unittest;
 
+option cc_enable_arenas = true;
 option optimize_for = SPEED;
+option csharp_namespace = "Google.ProtocolBuffers.TestProtos";
 
 // A message with message_set_wire_format.
 message TestMessageSet {
@@ -44,29 +47,6 @@ message TestMessageSet {
   extensions 4 to max;
 }
 
-message TestMessageSetContainer {
+message TestMessageSetWireFormatContainer {
   optional TestMessageSet message_set = 1;
 }
-
-message TestMessageSetExtension1 {
-  extend TestMessageSet {
-    optional TestMessageSetExtension1 message_set_extension = 1545008;
-  }
-  optional int32 i = 15;
-}
-
-message TestMessageSetExtension2 {
-  extend TestMessageSet {
-    optional TestMessageSetExtension2 message_set_extension = 1547769;
-  }
-  optional string str = 25;
-}
-
-// MessageSet wire format is equivalent to this.
-message RawMessageSet {
-  repeated group Item = 1 {
-    required int32 type_id = 2;
-    required bytes message = 3;
-  }
-}
-