Don't create new maps in CurrentMapForDeprecated.

src/hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1814 matching lines @@
   }
   // Handle either undetectable or monomorphic, not both.
   ASSERT(!types.Contains(CompareNilICStub::UNDETECTABLE) ||
          !types.Contains(CompareNilICStub::MONOMORPHIC_MAP));
   if (types.Contains(CompareNilICStub::UNDETECTABLE)) {
     if (needs_or) if_nil.Or();
     if_nil.If<HIsUndetectableAndBranch>(value);
   } else {
     if_nil.Then();
     if_nil.Else();
-    if (types.Contains(CompareNilICStub::MONOMORPHIC_MAP)) {
+    if (!map.is_null() && types.Contains(CompareNilICStub::MONOMORPHIC_MAP)) {
       BuildCheckNonSmi(value);
       // For ICs, the map checked below is a sentinel map that gets replaced by
       // the monomorphic map when the code is used as a template to generate a
       // new IC. For optimized functions, there is no sentinel map, the map
       // emitted below is the actual monomorphic map.
       BuildCheckMap(value, map);
     } else {
       if (kind == kNonStrictEquality) {
         if_nil.Deopt();
       }
@@ skipping 10623 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal