Extend API to allow setting length property for function templates.

src/factory.cc

 // Copyright 2012 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 1242 matching lines @@
       break;
   }
   ASSERT(type != INVALID_TYPE);
 
   Handle<JSFunction> result =
       NewFunction(Factory::empty_symbol(),
                   type,
                   instance_size,
                   code,
                   true);
+
+  // Set length.
+  result->shared()->set_length(obj->length());
+
   // Set class name.
   Handle<Object> class_name = Handle<Object>(obj->class_name());
   if (class_name->IsString()) {
     result->shared()->set_instance_class_name(*class_name);
     result->shared()->set_name(*class_name);
   }
 
   Handle<Map> map = Handle<Map>(result->initial_map());
 
   // Mark as undetectable if needed.
@@ skipping 170 matching lines @@
 
 
 Handle<Object> Factory::ToBoolean(bool value) {
   return Handle<Object>(value
                         ? isolate()->heap()->true_value()
                         : isolate()->heap()->false_value());
 }
 
 
 } }  // namespace v8::internal