First take on custom call generators.

src/parser.cc

 // Copyright 2006-2008 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 1946 matching lines @@
 
   // Instantiate the function and create a boilerplate function from it.
   Handle<JSFunction> fun = Utils::OpenHandle(*fun_template->GetFunction());
   const int literals = fun->NumberOfLiterals();
   Handle<Code> code = Handle<Code>(fun->shared()->code());
   Handle<Code> construct_stub = Handle<Code>(fun->shared()->construct_stub());
   Handle<JSFunction> boilerplate =
       Factory::NewFunctionBoilerplate(name, literals, code);
   boilerplate->shared()->set_construct_stub(*construct_stub);
 
-  // Copy the function data to the boilerplate. Used by
-  // builtins.cc:HandleApiCall to perform argument type checks and to
-  // find the right native code to call.
+  // Copy the function data to the boilerplate.
   boilerplate->shared()->set_function_data(fun->shared()->function_data());
   int parameters = fun->shared()->formal_parameter_count();
   boilerplate->shared()->set_formal_parameter_count(parameters);
 
   // TODO(1240846): It's weird that native function declarations are
   // introduced dynamically when we meet their declarations, whereas
   // other functions are setup when entering the surrounding scope.
   FunctionBoilerplateLiteral* lit =
       NEW(FunctionBoilerplateLiteral(boilerplate));
   VariableProxy* var = Declare(name, Variable::VAR, NULL, true, CHECK_OK);
@@ skipping 3164 matching lines @@
       parser.ParseLazy(script_source, name,
                        start_position, end_position, is_expression);
   return result;
 }
 
 
 #undef NEW
 
 
 } }  // namespace v8::internal