Index: twisted/web2/server.py
===================================================================
--- twisted/web2/server.py	(revision 18289)
+++ twisted/web2/server.py	(working copy)
@@ -156,7 +156,9 @@
         self.resources = []
         http.Request.__init__(self, *args, **kw)
 
-    def addResponseFilter(self, f, atEnd=False):
+    def addResponseFilter(self, f, atEnd=False, onlyOnce = False):
+        if onlyOnce and f in self.responseFilters:
+            return
         if atEnd:
             self.responseFilters.append(f)
         else:

Add patch that got lost during merge.
Add patch that got lost during merge.

git-svn-id: 81e381228600e5752b80483efd2b45b26c451ea2@198 e27351fd-9f3e-4f54-a53b-843176b1656c
