ExcServerVariants test: use constructors to initialize test structures

util/mach/child_port_server_test.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 49 matching lines @@
     token = kCheckInToken;
   }
 
   mach_msg_header_t Head;
   mach_msg_body_t msgh_body;
   mach_msg_port_descriptor_t port;
   NDR_record_t NDR;
   child_port_token_t token;
 };
 
-struct __attribute__((packed, aligned(4))) MIGReply {
+struct MIGReply : public mig_reply_error_t {
   MIGReply() {
     memset(this, 0x5a, sizeof(*this));
     RetCode = KERN_FAILURE;
   }
 
-  mach_msg_header_t Head;
-  NDR_record_t NDR;
-  kern_return_t RetCode;
-
   void Verify() {
     EXPECT_EQ(implicit_cast<mach_msg_bits_t>(MACH_MSGH_BITS(0, 0)),
               Head.msgh_bits);
     EXPECT_EQ(sizeof(*this), Head.msgh_size);
     EXPECT_EQ(kMachPortNull, Head.msgh_remote_port);
     EXPECT_EQ(kMachPortNull, Head.msgh_local_port);
     EXPECT_EQ(10111, Head.msgh_id);
     EXPECT_EQ(0, memcmp(&NDR, &NDR_record, sizeof(NDR)));
     EXPECT_EQ(MIG_NO_REPLY, RetCode);
   }
@@ skipping 34 matching lines @@
       reinterpret_cast<mach_msg_header_t*>(&reply),
       &destroy_complex_request));
   EXPECT_FALSE(destroy_complex_request);
 
   reply.Verify();
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace crashpad