Turn the NumberToStringStub into a hydrogen stub.

src/x64/code-stubs-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 190 matching lines @@
       MacroAssembler* masm,
       Register left,
       Register right,
       Register length,
       Register scratch,
       Label* chars_not_equal,
       Label::Distance near_jump = Label::kFar);
 };
 
 
-class NumberToStringStub: public PlatformCodeStub {
- public:
-  NumberToStringStub() { }
-
- private:
-  Major MajorKey() { return NumberToString; }
-  int MinorKey() { return 0; }
-
-  void Generate(MacroAssembler* masm);
-};
-
-
 class NameDictionaryLookupStub: public PlatformCodeStub {
  public:
   enum LookupMode { POSITIVE_LOOKUP, NEGATIVE_LOOKUP };
 
   NameDictionaryLookupStub(Register dictionary,
                            Register result,
                            Register index,
                            LookupMode mode)
       : dictionary_(dictionary), result_(result), index_(index), mode_(mode) { }
 
@@ skipping 285 matching lines @@
   RememberedSetAction remembered_set_action_;
   SaveFPRegsMode save_fp_regs_mode_;
   Label slow_;
   RegisterAllocation regs_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_CODE_STUBS_X64_H_