Add <stdarg.h> include required for va_start/va_end in GCC

net/disk_cache/blockfile/trace.cc

 // Copyright (c) 2011 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 "net/disk_cache/blockfile/trace.h"
 
+#include <stdarg.h>
 #include <stdio.h>
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/synchronization/lock.h"
 #include "net/disk_cache/blockfile/stress_support.h"
 
@@ skipping 166 matching lines @@
 void DestroyTrace(void) {
   s_trace_object = NULL;
 }
 
 void Trace(const char* format, ...) {
 }
 
 #endif  // ENABLE_TRACING
 
 }  // namespace disk_cache