Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs

 #region Copyright notice and license
 // 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
@@ skipping 233 matching lines @@
 
             // Validate that the dependencies we've been passed (as FileDescriptors) are actually the ones we
             // need.
             if (dependencies.Length != proto.Dependency.Count)
             {
                 throw new DescriptorValidationException(
                     result,
                     "Dependencies passed to FileDescriptor.BuildFrom() don't match " +
                     "those listed in the FileDescriptorProto.");
             }
+            for (int i = 0; i < proto.Dependency.Count; i++)
+            {
+                if (dependencies[i].Name != proto.Dependency[i])
+                {
+                    throw new DescriptorValidationException(
+                        result,
+                        "Dependencies passed to FileDescriptor.BuildFrom() don't match " +
+                        "those listed in the FileDescriptorProto. Expected: " +
+                        proto.Dependency[i] + " but was: " + dependencies[i].Name);
+                }
+            }
 
             result.CrossLink();
             return result;
         }
 
         private void CrossLink()
         {
             foreach (MessageDescriptor message in MessageTypes)
             {
                 message.CrossLink();
@@ skipping 59 matching lines @@
         /// annotations. While <c>descriptor.proto</c> is a proto2 file, it is built into the Google.Protobuf
         /// runtime for reflection purposes. The messages are internal to the runtime as they would require
         /// proto2 semantics for full support, but the file descriptor is available via this property. The
         /// C# codegen in protoc automatically uses this property when it detects a dependency on <c>descriptor.proto</c>.
         /// </remarks>
         /// <value>
         /// The file descriptor for <c>descriptor.proto</c>.
         /// </value>
         public static FileDescriptor DescriptorProtoFileDescriptor { get { return DescriptorReflection.Descriptor; } }
     }
-}
+}