Pass in the prototype to CreateApiFunction rather than setting it on the result.

src/factory.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_FACTORY_H_
 #define V8_FACTORY_H_
 
 #include "isolate.h"
 
 namespace v8 {
@@ skipping 434 matching lines @@
                                      MaybeHandle<Object>());
 
   Handle<JSFunction> NewFunctionWithPrototype(Handle<String> name,
                                               Handle<Object> prototype);
 
   Handle<JSFunction> NewFunctionFromSharedFunctionInfo(
       Handle<SharedFunctionInfo> function_info,
       Handle<Context> context,
       PretenureFlag pretenure = TENURED);
 
+  Handle<JSFunction> NewFunction(MaybeHandle<Object> maybe_prototype,
+                                 Handle<String> name,
+                                 InstanceType type,
+                                 int instance_size,
+                                 Handle<Code> code,
+                                 bool force_initial_map);
   Handle<JSFunction> NewFunction(Handle<String> name,
                                  InstanceType type,
                                  int instance_size,
                                  Handle<Code> code,
                                  bool force_initial_map);
 
   Handle<JSFunction> NewFunctionWithPrototype(Handle<String> name,
                                               InstanceType type,
                                               int instance_size,
                                               Handle<JSObject> prototype,
@@ skipping 67 matching lines @@
   }
 
   enum ApiInstanceType {
     JavaScriptObject,
     InnerGlobalObject,
     OuterGlobalObject
   };
 
   Handle<JSFunction> CreateApiFunction(
       Handle<FunctionTemplateInfo> data,
+      Handle<Object> prototype,
       ApiInstanceType type = JavaScriptObject);
 
   Handle<JSFunction> InstallMembers(Handle<JSFunction> function);
 
   // Installs interceptors on the instance.  'desc' is a function template,
   // and instance is an object instance created by the function of this
   // function template.
   MUST_USE_RESULT MaybeHandle<FunctionTemplateInfo> ConfigureInstance(
       Handle<FunctionTemplateInfo> desc, Handle<JSObject> instance);
 
@@ skipping 119 matching lines @@
   // the string representation of the number.  Otherwise return undefined.
   Handle<Object> GetNumberStringCache(Handle<Object> number);
 
   // Update the cache with a new number-string pair.
   void SetNumberStringCache(Handle<Object> number, Handle<String> string);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_FACTORY_H_