Unify the handling of comparinsons against null and undefined.

src/hydrogen.h

Index: src/hydrogen.h
===================================================================
--- src/hydrogen.h	(revision 9305)
+++ src/hydrogen.h	(working copy)
@@ -910,13 +910,13 @@
                                   HValue* receiver,
                                   SmallMapList* types,
                                   Handle<String> name);
-  void HandleLiteralCompareTypeof(CompareOperation* compare_expr,
-                                  Expression* expr,
+  bool TryLiteralCompare(CompareOperation* expr);
+  void HandleLiteralCompareTypeof(CompareOperation* expr,
+                                  Expression* sub_expr,
                                   Handle<String> check);
-  void HandleLiteralCompareUndefined(CompareOperation* compare_expr,
-                                     Expression* expr);
-  void HandleLiteralCompareNull(CompareOperation* compare_expr,
-                                Expression* expr);
+  void HandleLiteralCompareNil(CompareOperation* expr,
+                               Expression* sub_expr,
+                               NilValue nil);
 
   HStringCharCodeAt* BuildStringCharCodeAt(HValue* context,
                                            HValue* string,