Fix GCC build for target 'all'

chrome/browser/media/cast_remoting_connector_fuzzertest.cc

 // Copyright 2016 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 "chrome/browser/media/cast_remoting_connector_messaging.h"
 
 // Entry point for LibFuzzer.
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   // All of the input is used as the text message.
   const std::string text_message(reinterpret_cast<const char*>(data), size);
 
   // Compute an arbitrary, but deterministic "expected session ID."
   const unsigned int session_id = size / 4;
 
   // Make sure the compiler does not try to optimize-away calls by storing their
   // results in a volatile variable.
   volatile unsigned int ignored_result;
+  (void)ignored_result;
 
   using Messaging = CastRemotingConnectorMessaging;
 
   if (Messaging::IsMessageForSession(
           text_message, Messaging::kStartedStreamsMessageFormatPartial,
           session_id)) {
     ignored_result = Messaging::GetStreamIdFromStartedMessage(
         text_message, Messaging::kStartedStreamsMessageAudioIdSpecifier);
     ignored_result = Messaging::GetStreamIdFromStartedMessage(
         text_message, Messaging::kStartedStreamsMessageVideoIdSpecifier);
   }
   ignored_result = Messaging::IsMessageForSession(
       text_message, Messaging::kFailedMessageFormat, session_id);
   ignored_result = Messaging::IsMessageForSession(
       text_message, Messaging::kStoppedMessageFormat, session_id);
 
   return 0;
 }