Use Arguments object in C builtins, instead of __argc__ and __argv__.

src/x64/frames-x64.h

 // Copyright 2009 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 42 matching lines @@
   static const int kStateOffset = 2 * kPointerSize;
   static const int kPCOffset    = 3 * kPointerSize;
 
   static const int kSize = 4 * kPointerSize;
 };
 
 
 class EntryFrameConstants : public AllStatic {
  public:
   static const int kCallerFPOffset      = -10 * kPointerSize;
-  // TODO(X64): Add unit test for kArgvOffset.
-  static const int kArgvOffset          = 5 * kPointerSize;
+  static const int kArgvOffset          = 6 * kPointerSize;
 };
 
 
 class ExitFrameConstants : public AllStatic {
  public:
   static const int kDebugMarkOffset = -2 * kPointerSize;
   static const int kSPOffset        = -1 * kPointerSize;
 
   static const int kCallerFPOffset  = +0 * kPointerSize;
   static const int kCallerPCOffset  = +1 * kPointerSize;
@@ skipping 41 matching lines @@
 
 
 inline Object* JavaScriptFrame::function_slot_object() const {
   const int offset = JavaScriptFrameConstants::kFunctionOffset;
   return Memory::Object_at(fp() + offset);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_FRAMES_X64_H_