Update //third_party/protobuf to version 3.

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

+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 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 System.Reflection;
+using Google.Protobuf.Compatibility;
+
+namespace Google.Protobuf.Reflection
+{
+    /// <summary>
+    /// Reflection access for a oneof, allowing clear and "get case" actions.
+    /// </summary>
+    public sealed class OneofAccessor
+    {
+        private readonly Func<IMessage, int> caseDelegate;
+        private readonly Action<IMessage> clearDelegate;
+        private OneofDescriptor descriptor;
+
+        internal OneofAccessor(PropertyInfo caseProperty, MethodInfo clearMethod, OneofDescriptor descriptor) 
+        {
+            if (!caseProperty.CanRead)
+            {
+                throw new ArgumentException("Cannot read from property");
+            }
+            this.descriptor = descriptor;
+            caseDelegate = ReflectionUtil.CreateFuncIMessageT<int>(caseProperty.GetGetMethod());
+
+            this.descriptor = descriptor;
+            clearDelegate = ReflectionUtil.CreateActionIMessage(clearMethod);
+        }
+
+        /// <summary>
+        /// Gets the descriptor for this oneof.
+        /// </summary>
+        /// <value>
+        /// The descriptor of the oneof.
+        /// </value>
+        public OneofDescriptor Descriptor { get { return descriptor; } }
+
+        /// <summary>
+        /// Clears the oneof in the specified message.
+        /// </summary>
+        public void Clear(IMessage message)
+        {
+            clearDelegate(message);
+        }
+
+        /// <summary>
+        /// Indicates which field in the oneof is set for specified message
+        /// </summary>
+        public FieldDescriptor GetCaseFieldDescriptor(IMessage message)
+        {
+            int fieldNumber = caseDelegate(message);
+            if (fieldNumber > 0)
+            {
+                return descriptor.ContainingType.FindFieldByNumber(fieldNumber);
+            }
+            return null;
+        }
+    }
+}