Explicitly #include <unistd.h> to avoid a compile error

base/message_pump_libevent.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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 "base/message_pump_libevent.h"
 
 #include <errno.h>
 #include <fcntl.h>
+#include <unistd.h>
 
 #include "base/auto_reset.h"
 #include "base/compiler_specific.h"
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #if defined(OS_MACOSX)
 #include "base/mac/scoped_nsautorelease_pool.h"
 #endif
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
@@ skipping 357 matching lines @@
   // Remove and discard the wakeup byte.
   char buf;
   int nread = HANDLE_EINTR(read(socket, &buf, 1));
   DCHECK_EQ(nread, 1);
   that->processed_io_events_ = true;
   // Tell libevent to break out of inner loop.
   event_base_loopbreak(that->event_base_);
 }
 
 }  // namespace base