Update //third_party/protobuf to version 3.

third_party/protobuf/csharp/src/Google.Protobuf/IMessage.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
+// 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
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using Google.Protobuf.Reflection;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Interface for a Protocol Buffers message, supporting
+    /// basic operations required for serialization.
+    /// </summary>
+    public interface IMessage
+    {
+        /// <summary>
+        /// Merges the data from the specified coded input stream with the current message.
+        /// </summary>
+        /// <remarks>See the user guide for precise merge semantics.</remarks>
+        /// <param name="input"></param>
+        void MergeFrom(CodedInputStream input);
+
+        /// <summary>
+        /// Writes the data to the given coded output stream.
+        /// </summary>
+        /// <param name="output">Coded output stream to write the data to. Must not be null.</param>
+        void WriteTo(CodedOutputStream output);
+
+        /// <summary>
+        /// Calculates the size of this message in Protocol Buffer wire format, in bytes.
+        /// </summary>
+        /// <returns>The number of bytes required to write this message
+        /// to a coded output stream.</returns>
+        int CalculateSize();
+
+        /// <summary>
+        /// Descriptor for this message. All instances are expected to return the same descriptor,
+        /// and for generated types this will be an explicitly-implemented member, returning the
+        /// same value as the static property declared on the type.
+        /// </summary>
+        MessageDescriptor Descriptor { get; }
+    }
+
+    /// <summary>
+    /// Generic interface for a Protocol Buffers message,
+    /// where the type parameter is expected to be the same type as
+    /// the implementation class.
+    /// </summary>
+    /// <typeparam name="T">The message type.</typeparam>
+    public interface IMessage<T> : IMessage, IEquatable<T>, IDeepCloneable<T> where T : IMessage<T>
+    {
+        /// <summary>
+        /// Merges the given message into this one.
+        /// </summary>
+        /// <remarks>See the user guide for precise merge semantics.</remarks>
+        /// <param name="message">The message to merge with this one. Must not be null.</param>
+        void MergeFrom(T message);
+    }
+}