Fixed an XP change that wasn't XP (_MAX_PATH is already defined on the mac)

git-svn-id: svn://10.0.0.236/trunk@9195 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/webshell/tests/viewer/nsViewerApp.cpp

@@ -516,8 +516,10 @@ nsViewerApp::AfterDispatch()
 #include "nsIURL.h"
 
 #ifndef XP_PC
+#ifndef XP_MAC
 #define _MAX_PATH 512
 #endif
+#endif
 
 #define DEBUG_EMPTY "(none)"
 static PRInt32 gDebugRobotLoads = 5000;