Clean up remaining unused globals (on mac).

remoting/host/remoting_me2me_host.cc

Index: remoting/host/remoting_me2me_host.cc
diff --git a/remoting/host/remoting_me2me_host.cc b/remoting/host/remoting_me2me_host.cc
index 9ed3383974cdc763e9fd390aa02d0df60022d6d9..97886e9e89c997d93f0aff30145f6579cf9f3c6a 100644
--- a/remoting/host/remoting_me2me_host.cc
+++ b/remoting/host/remoting_me2me_host.cc
@@ -103,9 +103,11 @@ namespace {
 // This is used for tagging system event logs.
 const char kApplicationName[] = "chromoting";
 
+#if defined(OS_LINUX)
 // The command line switch used to pass name of the pipe to capture audio on
 // linux.
 const char kAudioPipeSwitchName[] = "audio-pipe-name";
+#endif  // defined(OS_LINUX)
 
 // The command line switch used by the parent to request the host to signal it
 // when it is successfully started.