Revert "third_party/protobuf: Update to HEAD (f52e188fe4)"

third_party/protobuf/src/google/protobuf/map_unittest.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 65 matching lines @@
   map<int32, int32> map2 = 2;
 }
 
 
 enum MapEnum {
   MAP_ENUM_FOO = 0;
   MAP_ENUM_BAR = 1;
   MAP_ENUM_BAZ = 2;
 }
 
-// Test embedded message with required fields
+// Test embeded message with required fields
 message TestRequiredMessageMap {
   map<int32, TestRequired> map_field = 1;
 }
 
 message TestArenaMap {
   map<int32   , int32   > map_int32_int32       = 1;
   map<int64   , int64   > map_int64_int64       = 2;
   map<uint32  , uint32  > map_uint32_uint32     = 3;
   map<uint64  , uint64  > map_uint64_uint64     = 4;
   map<sint32  , sint32  > map_sint32_sint32     = 5;
@@ skipping 23 matching lines @@
 }
 
 // Previously, message cannot contain map field called "entry".
 message MessageContainingMapCalledEntry {
   map<int32, int32> entry = 1;
 }
 
 message TestRecursiveMapMessage {
   map<string, TestRecursiveMapMessage> a = 1;
 }