Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/java/core/src/test/proto/com/google/protobuf/test_bad_identifiers.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 25 matching lines @@
 syntax = "proto2";
 
 // Some generic_services option(s) added automatically.
 // See:  http://go/proto2-generic-services-default
 option java_generic_services = true;   // auto-added
 
 package io_protocol_tests;
 
 option java_package = "com.google.protobuf";
 option java_outer_classname = "TestBadIdentifiersProto";
+option java_generate_equals_and_hash = true;
 
 message TestMessage {
   optional string cached_size = 1;
   optional string serialized_size = 2;
   optional string class = 3;
 }
 
 message Descriptor {
   option no_standard_descriptor_accessor = true;
   optional string descriptor = 1;
@@ skipping 103 matching lines @@
   }  // NO_PROTO3
 }
 
 message TestMapField {
   message MapField {}
   message Pair {}
   message Message {}
 
   map<int32, int32> map_field = 1;
 }