Update third_party/protobuf to protobuf-v3.0.0-beta-3

third_party/protobuf/csharp/src/Google.Protobuf/Preconditions.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;
-
-namespace Google.Protobuf
-{
-    /// <summary>
-    /// Helper methods for throwing exceptions
-    /// </summary>
-    public static class Preconditions
-    {
-        /// <summary>
-        /// Throws an ArgumentNullException if the given value is null, otherwise
-        /// return the value to the caller.
-        /// </summary>
-        public static T CheckNotNull<T>(T value, string name) where T : class
-        {
-            if (value == null)
-            {
-                throw new ArgumentNullException(name);
-            }
-            return value;
-        }
-
-        /// <summary>
-        /// Throws an ArgumentNullException if the given value is null, otherwise
-        /// return the value to the caller.
-        /// </summary>
-        /// <remarks>
-        /// This is equivalent to <see cref="CheckNotNull{T}(T, string)"/> but without the type parameter
-        /// constraint. In most cases, the constraint is useful to prevent you from calling CheckNotNull
-        /// with a value type - but it gets in the way if either you want to use it with a nullable
-        /// value type, or you want to use it with an unconstrained type parameter.
-        /// </remarks>
-        internal static T CheckNotNullUnconstrained<T>(T value, string name)
-        {
-            if (value == null)
-            {
-                throw new ArgumentNullException(name);
-            }
-            return value;
-        }
-    }
-}