Add Directory.systemTemp getter to replace createSystemTemp().

sdk/lib/io/io_service.dart

Index: sdk/lib/io/io_service.dart
diff --git a/sdk/lib/io/io_service.dart b/sdk/lib/io/io_service.dart
index 037cdd1cfbc85a413ed10a1706ca0d3cd88413ea..bf4b42b5eb63e8c3dcfc1bc79b33efc00a5965eb 100644
--- a/sdk/lib/io/io_service.dart
+++ b/sdk/lib/io/io_service.dart
@@ -38,12 +38,11 @@ const int _DIRECTORY_CREATE = 29;
 const int _DIRECTORY_DELETE = 30;
 const int _DIRECTORY_EXISTS = 31;
 const int _DIRECTORY_CREATE_TEMP = 32;
-const int _DIRECTORY_CREATE_SYSTEM_TEMP = 33;
-const int _DIRECTORY_LIST_START = 34;
-const int _DIRECTORY_LIST_NEXT = 35;
-const int _DIRECTORY_LIST_STOP = 36;
-const int _DIRECTORY_RENAME = 37;
-const int _SSL_PROCESS_FILTER = 38;
+const int _DIRECTORY_LIST_START = 33;
+const int _DIRECTORY_LIST_NEXT = 34;
+const int _DIRECTORY_LIST_STOP = 35;
+const int _DIRECTORY_RENAME = 36;
+const int _SSL_PROCESS_FILTER = 37;
 
 class _IOService {
   external static Future dispatch(int request, List data);