third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/java/util/src/test/proto/com/google/protobuf/util/json_test.proto

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 // 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
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
@@ skipping 106 matching lines @@
   repeated string repeated_string = 44;
   repeated bytes repeated_bytes = 45;
   repeated NestedMessage repeated_nested_message = 48;
   repeated NestedEnum repeated_nested_enum = 51;
 }
 
 message TestOneof {
   oneof oneof_field {
     int32 oneof_int32 = 1;
     TestAllTypes.NestedMessage oneof_nested_message = 2;
+    google.protobuf.NullValue oneof_null_value = 3;
   }
 }
 
 message TestMap {
   // Instead of testing all combinations (too many), we only make sure all
   // valid types have been used at least in one field as key and in one
   // field as value.
   map<int32, int32> int32_to_int32_map = 1;
   map<int64, int32> int64_to_int32_map = 2;
   map<uint32, int32> uint32_to_int32_map = 3;
@@ skipping 50 matching lines @@
 }
 
 message TestStruct {
   google.protobuf.Struct struct_value = 1;
   google.protobuf.Value value = 2;
   google.protobuf.ListValue list_value = 3;
 }
 
 message TestAny {
   google.protobuf.Any any_value = 1;
+  map<string, google.protobuf.Any> any_map = 2;
 }
 
 message TestCustomJsonName {
   int32 value = 1 [json_name = "@value"];
 }
+
+message TestRecursive {
+  int32 value = 1;
+  TestRecursive nested = 2;
+}