[turbofan] Fix control reducer for dead loops.

src/compiler/control-reducer.h

Index: src/compiler/control-reducer.h
diff --git a/src/compiler/control-reducer.h b/src/compiler/control-reducer.h
index 1bed84a5cb13b1d7c50044d5bbc352ed8a1e7482..bcbd80e9165c6fefea45f531693101ed7ac49ada 100644
--- a/src/compiler/control-reducer.h
+++ b/src/compiler/control-reducer.h
@@ -28,15 +28,16 @@ class ControlReducer {
   // Trim nodes in the graph that are not reachable from end.
   static void TrimGraph(Zone* zone, JSGraph* graph);
 
+  // Reduces a single merge node and attached phis.
+  static Node* ReduceMerge(JSGraph* graph, CommonOperatorBuilder* builder,
+                           Node* node);
+
   // Testing interface.
   static Node* ReducePhiForTesting(JSGraph* graph,
                                    CommonOperatorBuilder* builder, Node* node);
   static Node* ReduceIfNodeForTesting(JSGraph* graph,
                                       CommonOperatorBuilder* builder,
                                       Node* node);
-  static Node* ReduceMergeForTesting(JSGraph* graph,
-                                     CommonOperatorBuilder* builder,
-                                     Node* node);
 };
 }
 }