removed OnResponseCompleted from Owin

Author: ajaybhargavb

src/Microsoft.AspNet.Owin/OwinConstants.cs

@@ -70,7 +70,6 @@ internal static class CommonKeys
             public const string AppName = "host.AppName";
             public const string Capabilities = "server.Capabilities";
             public const string OnSendingHeaders = "server.OnSendingHeaders";
-            public const string OnResponseCompleted = "server.OnResponseCompleted";
             public const string OnAppDisposing = "host.OnAppDisposing";
             public const string Scheme = "scheme";
             public const string Host = "host";

src/Microsoft.AspNet.Owin/OwinEnvironment.cs

@@ -62,8 +62,6 @@ public OwinEnvironment(HttpContext context)
                 { OwinConstants.ResponseHeaders, new FeatureMap<IHttpResponseFeature>(feature => feature.Headers, (feature, value) => feature.Headers = (IDictionary<string, string[]>)value) },
                 { OwinConstants.ResponseBody, new FeatureMap<IHttpResponseFeature>(feature => feature.Body, () => Stream.Null, (feature, value) => feature.Body = (Stream)value) },
                 { OwinConstants.CommonKeys.OnSendingHeaders, new FeatureMap<IHttpResponseFeature>(feature => new Action<Action<object>, object>(feature.OnSendingHeaders)) },
-                {OwinConstants.CommonKeys.OnResponseCompleted, new FeatureMap<IHttpResponseFeature>(feature => new Action<Action<object>, object>
-                  (feature.OnResponseCompleted)) },
 
                 { OwinConstants.CommonKeys.LocalPort, new FeatureMap<IHttpConnectionFeature>(feature => feature.LocalPort.ToString(CultureInfo.InvariantCulture),
                     (feature, value) => feature.LocalPort = Convert.ToInt32(value, CultureInfo.InvariantCulture)) },

src/Microsoft.AspNet.Owin/OwinFeatureCollection.cs

@@ -157,12 +157,7 @@ void IHttpResponseFeature.OnSendingHeaders(Action<object> callback, object state
 
         void IHttpResponseFeature.OnResponseCompleted(Action<object> callback, object state)
         {
-            var register = Prop<Action<Action<object>, object>>(OwinConstants.CommonKeys.OnResponseCompleted);
-            if (register == null)
-            {
-                throw new NotSupportedException(OwinConstants.CommonKeys.OnResponseCompleted);
-            }
-            register(callback, state);
+            throw new NotSupportedException();
         }
 
         IPAddress IHttpConnectionFeature.RemoteIpAddress