nacl: Fix a bunch of compiler warnings

ipc/ipc_channel.cc

 // 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 "ipc/ipc_channel.h"
 
 #include <limits>
 
 #include "base/atomic_sequence_num.h"
 #include "base/process_util.h"
 #include "base/rand_util.h"
 #include "base/stringprintf.h"
 
+#if !defined(OS_NACL)
 namespace {
 
 // Global atomic used to guarantee channel IDs are unique.
 base::StaticAtomicSequenceNumber g_last_id;
 
 }  // namespace
+#endif
 
 namespace IPC {
 
 // static
 std::string Channel::GenerateUniqueRandomChannelID() {
   // Note: the string must start with the current process id, this is how
   // some child processes determine the pid of the parent.
   //
   // This is composed of a unique incremental identifier, the process ID of
   // the creator, an identifier for the child instance, and a strong random
   // component. The strong random component prevents other processes from
   // hijacking or squatting on predictable channel names.
 
 #if !defined(OS_NACL)
   int process_id = base::GetCurrentProcId();
   return base::StringPrintf("%d.%u.%d",
       process_id,
       g_last_id.GetNext(),
       base::RandInt(0, std::numeric_limits<int32>::max()));
 #else
   return std::string();
 #endif
 }
 
 }  // namespace IPC