Fix build warnings in NaCl IPC proxy.

ipc/ipc_channel.cc

Index: ipc/ipc_channel.cc
===================================================================
--- ipc/ipc_channel.cc	(revision 158695)
+++ ipc/ipc_channel.cc	(working copy)
@@ -32,15 +32,11 @@
   // 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