Modify ALLOW_UNUSED to allow enabling unused local warnings on MSVC.

mojo/edk/system/data_pipe.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/system/data_pipe.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 424 matching lines @@
                     MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_MAY_DISCARD)),
       element_num_bytes_(validated_options.element_num_bytes),
       capacity_num_bytes_(validated_options.capacity_num_bytes),
       producer_open_(true),
       consumer_open_(true),
       producer_waiter_list_(has_local_producer ? new WaiterList() : nullptr),
       consumer_waiter_list_(has_local_consumer ? new WaiterList() : nullptr),
       producer_two_phase_max_num_bytes_written_(0),
       consumer_two_phase_max_num_bytes_read_(0) {
   // Check that the passed in options actually are validated.
-  MojoCreateDataPipeOptions unused ALLOW_UNUSED = {0};
+  MojoCreateDataPipeOptions unused = {0};
   DCHECK_EQ(ValidateCreateOptions(MakeUserPointer(&validated_options), &unused),
             MOJO_RESULT_OK);
 }
 
 DataPipe::~DataPipe() {
   DCHECK(!producer_open_);
   DCHECK(!consumer_open_);
   DCHECK(!producer_waiter_list_);
   DCHECK(!consumer_waiter_list_);
 }
 
 void DataPipe::AwakeProducerWaitersForStateChangeNoLock(
     const HandleSignalsState& new_producer_state) {
   lock_.AssertAcquired();
   if (!has_local_producer_no_lock())
     return;
   producer_waiter_list_->AwakeWaitersForStateChange(new_producer_state);
 }
 
 void DataPipe::AwakeConsumerWaitersForStateChangeNoLock(
     const HandleSignalsState& new_consumer_state) {
   lock_.AssertAcquired();
   if (!has_local_consumer_no_lock())
     return;
   consumer_waiter_list_->AwakeWaitersForStateChange(new_consumer_state);
 }
 
 }  // namespace system
 }  // namespace mojo