[compiler] Drop the CompareNilIC.

src/crankshaft/hydrogen.h

Index: src/crankshaft/hydrogen.h
diff --git a/src/crankshaft/hydrogen.h b/src/crankshaft/hydrogen.h
index a855f081dfe209b9f3c653d9b5b8d61057db4ebd..f751073ab1ddaa69ea938f759f9d873a5a6be65e 100644
--- a/src/crankshaft/hydrogen.h
+++ b/src/crankshaft/hydrogen.h
@@ -1833,11 +1833,6 @@ class HGraphBuilder {
 
   HValue* BuildElementIndexHash(HValue* index);
 
-  enum MapEmbedding { kEmbedMapsDirectly, kEmbedMapsViaWeakCells };
-
-  void BuildCompareNil(HValue* value, Type* type, HIfContinuation* continuation,
-                       MapEmbedding map_embedding = kEmbedMapsDirectly);
-
   void BuildCreateAllocationMemento(HValue* previous_object,
                                     HValue* previous_object_size,
                                     HValue* payload);