[turbofan] Turn JSContextSpecializer into an AdvancedReducer.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index 1d9b329c5be6354eeec9f8dcb3031bc2f6da32b7..e7c76aabc3934d7212c714197bd75ba34470b87a 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -496,8 +496,8 @@ struct ContextSpecializerPhase {
   static const char* phase_name() { return "context specializing"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
-    JSContextSpecializer spec(data->jsgraph());
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
+    JSContextSpecializer spec(&graph_reducer, data->jsgraph());
     AddReducer(data, &graph_reducer, &spec);
     graph_reducer.ReduceGraph();
   }