Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/src/google/protobuf/compiler/csharp/csharp_generator.cc

 // 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 @@
   struct Options cli_options;
 
   for (int i = 0; i < options.size(); i++) {
     if (options[i].first == "file_extension") {
       cli_options.file_extension = options[i].second;
     } else if (options[i].first == "base_namespace") {
       cli_options.base_namespace = options[i].second;
       cli_options.base_namespace_specified = true;
     } else if (options[i].first == "internal_access") {
       cli_options.internal_access = true;
+    } else if (options[i].first == "legacy_enum_values") {
+      // TODO: Remove this before final release
+      cli_options.legacy_enum_values = true;
     } else {
       *error = "Unknown generator option: " + options[i].first;
       return false;
     }
   }
 
   string filename_error = "";
   std::string filename = GetOutputFile(file,
       cli_options.file_extension,
       cli_options.base_namespace_specified,
@@ skipping 10 matching lines @@
 
   GenerateFile(file, &printer, &cli_options);
 
   return true;
 }
 
 }  // namespace csharp
 }  // namespace compiler
 }  // namespace protobuf
 }  // namespace google