Fix for codeplex-2136 - ControllerContext.IsChildAction returns false for

an attribute routed action while inside Controller.Initialize.

The issue is that we haven't selected the 'real' action yet and promoted
its route data when we run Controller.Initialize.

This change adds the required value to data tokens so that we return the
right value inside Initialize.

src/System.Web.Mvc/Html/ChildActionExtensions.cs

@@ -153,7 +153,17 @@ namespace System.Web.Mvc.Html
             // 'direct route' routedata to reach it.
             if (route.IsDirectRoute())
             {
-                return RouteCollectionRoute.CreateDirectRouteMatch(route, new List<RouteData>() { routeData });
+                // Codeplex-2136 - ControllerContext.IsChildAction returns false inside Controller.Initialize()
+                //
+                // We're constructing a 'temp' route data to wrap the route data for the match we're invoking via
+                // an attribute route. The ControllerContext will look at datatokens to see if it's being invoked
+                // as a child action. 
+                //
+                // By sticking the view context on both route data ControllerContext will do the right thing
+                // at all parts of the pipeline.
+                var directRouteData = RouteCollectionRoute.CreateDirectRouteMatch(route, new List<RouteData>() { routeData });
+                directRouteData.DataTokens[ControllerContext.ParentActionViewContextToken] = parentViewContext;
+                return directRouteData;
             }
             else
             {