Additional minor cleanup regarding CallWrapper: Use the null object pattern.

src/mips/macro-assembler-mips.h

 // Copyright 2010 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 569 matching lines @@
                                     Register scratch);
 
   // -------------------------------------------------------------------------
   // JavaScript invokes
 
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeCode(Register code,
                   const ParameterCount& expected,
                   const ParameterCount& actual,
                   InvokeFlag flag,
-                  CallWrapper* call_wrapper = NULL);
+                  const CallWrapper& call_wrapper = NullCallWrapper());
 
   void InvokeCode(Handle<Code> code,
                   const ParameterCount& expected,
                   const ParameterCount& actual,
                   RelocInfo::Mode rmode,
                   InvokeFlag flag);
 
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function,
                       const ParameterCount& actual,
                       InvokeFlag flag,
-                      CallWrapper* call_wrapper = NULL);
+                      const CallWrapper& call_wrapper = NullCallWrapper());
 
   void InvokeFunction(JSFunction* function,
                       const ParameterCount& actual,
                       InvokeFlag flag);
 
 
   void IsObjectJSObjectType(Register heap_object,
                             Register map,
                             Register scratch,
                             Label* fail);
@@ skipping 149 matching lines @@
   void CallCFunction(ExternalReference function, int num_arguments);
   void CallCFunction(Register function, Register scratch, int num_arguments);
 
   // Jump to the builtin routine.
   void JumpToExternalReference(const ExternalReference& builtin);
 
   // Invoke specified builtin JavaScript function. Adds an entry to
   // the unresolved list if the name does not resolve.
   void InvokeBuiltin(Builtins::JavaScript id,
                      InvokeFlag flag,
-                     CallWrapper* call_wrapper = NULL);
+                     const CallWrapper& call_wrapper = NullCallWrapper());
 
   // Store the code object for the given builtin in the target register and
   // setup the function in a1.
   void GetBuiltinEntry(Register target, Builtins::JavaScript id);
 
   // Store the function for the given builtin in the target register.
   void GetBuiltinFunction(Register target, Builtins::JavaScript id);
 
   struct Unresolved {
     int pc;
@@ skipping 162 matching lines @@
             Register r1 = zero_reg, const Operand& r2 = Operand(zero_reg),
             BranchDelaySlot bd = PROTECT);
 
   // Helper functions for generating invokes.
   void InvokePrologue(const ParameterCount& expected,
                       const ParameterCount& actual,
                       Handle<Code> code_constant,
                       Register code_reg,
                       Label* done,
                       InvokeFlag flag,
-                      CallWrapper* call_wrapper = NULL);
+                      const CallWrapper& call_wrapper = NullCallWrapper());
 
   // Get the code for the given builtin. Returns if able to resolve
   // the function in the 'resolved' flag.
   Handle<Code> ResolveBuiltin(Builtins::JavaScript id, bool* resolved);
 
   // Activation support.
   void EnterFrame(StackFrame::Type type);
   void LeaveFrame(StackFrame::Type type);
 
   void InitializeNewString(Register string,
@@ skipping 65 matching lines @@
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_MIPS_MACRO_ASSEMBLER_MIPS_H_