third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/objectivec/Tests/unittest_extension_chain_f.proto

 // Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
-// https://developers.google.com/protocol-buffers/
+// Copyright 2016 Google Inc.  All rights reserved.
 //
 // 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.
 
-// Proto to test proto3 struct.
-syntax = "proto3";
+syntax = "proto2";
 
-package google.protobuf.testing.structs;
-option java_package = "com.google.protobuf.testing.structs";
+package protobuf_unittest;
 
-import "google/protobuf/struct.proto";
+import "unittest_extension_chain_g.proto";
 
-message StructType {
-  google.protobuf.Struct object = 1;
+// The Root for this file should just be merging in the extensions from C's
+// Root (because G doens't define anything itself).
+
+// The generated source will also have to directly import C's .h file so it can
+// compile the reference to C's Root class.
+
+message ChainFMessage {
+  optional ChainGMessage g = 1;
 }
-
-service TestService {
-  rpc Call(StructType) returns (StructType);
-}