Update //third_party/protobuf to version 3.

third_party/protobuf/src/google/protobuf/io/zero_copy_stream_impl.h

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
-// http://code.google.com/p/protobuf/
+// 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.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
 // in the documentation and/or other materials provided with the
@@ skipping 323 matching lines @@
   // implements ZeroCopyInputStream ----------------------------------
   bool Next(const void** data, int* size);
   void BackUp(int count);
   bool Skip(int count);
   int64 ByteCount() const;
 
 
  private:
   ZeroCopyInputStream* input_;
   int64 limit_;  // Decreases as we go, becomes negative if we overshoot.
+  int64 prior_bytes_read_;  // Bytes read on underlying stream at construction
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(LimitingInputStream);
 };
 
 // ===================================================================
 
 }  // namespace io
 }  // namespace protobuf
 
 }  // namespace google
 #endif  // GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__