Add boolean flag to HChange and LNumberUntagD to not convert undefined to NaN.

src/x64/lithium-x64.h

 // Copyright 2011 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 1633 matching lines @@
 };
 
 
 class LNumberUntagD: public LTemplateInstruction<1, 1, 0> {
  public:
   explicit LNumberUntagD(LOperand* value) {
     inputs_[0] = value;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(NumberUntagD, "double-untag")
+  DECLARE_HYDROGEN_ACCESSOR(Change);
 };
 
 
 class LSmiUntag: public LTemplateInstruction<1, 1, 0> {
  public:
   LSmiUntag(LOperand* value, bool needs_check)
       : needs_check_(needs_check) {
     inputs_[0] = value;
   }
 
@@ skipping 639 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_