Update //third_party/protobuf to version 3.

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

Index: third_party/protobuf/csharp/src/Google.Protobuf/Reflection/IDescriptor.cs
diff --git a/third_party/protobuf/python/google/protobuf/internal/more_extensions_dynamic.proto b/third_party/protobuf/csharp/src/Google.Protobuf/Reflection/IDescriptor.cs
similarity index 68%
copy from third_party/protobuf/python/google/protobuf/internal/more_extensions_dynamic.proto
copy to third_party/protobuf/csharp/src/Google.Protobuf/Reflection/IDescriptor.cs
index df98ac4bd1929fda636c9e2fce1a9184ebf5d472..318d58c968a58a35a3ccd45ee1c7b1f0df275546 100644
--- a/third_party/protobuf/python/google/protobuf/internal/more_extensions_dynamic.proto
+++ b/third_party/protobuf/csharp/src/Google.Protobuf/Reflection/IDescriptor.cs
@@ -1,6 +1,7 @@
+#region Copyright notice and license
 // 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
@@ -27,23 +28,28 @@
 // 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
 
-// Author: jasonh@google.com (Jason Hsueh)
-//
-// This file is used to test a corner case in the CPP implementation where the
-// generated C++ type is available for the extendee, but the extension is
-// defined in a file whose C++ type is not in the binary.
-
-
-import "google/protobuf/internal/more_extensions.proto";
-
-package google.protobuf.internal;
+namespace Google.Protobuf.Reflection
+{
+    /// <summary>
+    /// Interface implemented by all descriptor types.
+    /// </summary>
+    public interface IDescriptor
+    {
+        /// <summary>
+        /// Returns the name of the entity (message, field etc) being described.
+        /// </summary>
+        string Name { get; }
 
-message DynamicMessageType {
-  optional int32 a = 1;
-}
+        /// <summary>
+        /// Returns the fully-qualified name of the entity being described.
+        /// </summary>
+        string FullName { get; }
 
-extend ExtendedMessage {
-  optional int32 dynamic_int32_extension = 100;
-  optional DynamicMessageType dynamic_message_extension = 101;
-}
+        /// <summary>
+        /// Returns the descriptor for the .proto file that this entity is part of.
+        /// </summary>
+        FileDescriptor File { get; }
+    }    
+}