Pass in the map while creating JSFunction, and set prototype in the client.

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 658 matching lines @@
 
   // Creates a code object that is not yet fully initialized yet.
   inline Handle<Code> NewCodeRaw(int object_size, bool immovable);
 
   // Initializes a function with a shared part and prototype.
   // Note: this code was factored out of NewFunction such that other parts of
   // the VM could use it. Specifically, a function that creates instances of
   // type JS_FUNCTION_TYPE benefit from the use of this function.
   inline void InitializeFunction(Handle<JSFunction> function,
                                  Handle<SharedFunctionInfo> info,
-                                 Handle<Context> context,
-                                 MaybeHandle<Object> maybe_prototype);
+                                 Handle<Context> context);
 
   // Creates a function initialized with a shared part.
-  inline Handle<JSFunction> NewFunction(Handle<SharedFunctionInfo> info,
+  inline Handle<JSFunction> NewFunction(Handle<Map> map,
+                                        Handle<SharedFunctionInfo> info,
                                         Handle<Context> context,
-                                        MaybeHandle<Object> maybe_prototype,
                                         PretenureFlag pretenure = TENURED);
 
   // Create a new map cache.
   Handle<MapCache> NewMapCache(int at_least_space_for);
 
   // Update the map cache in the native context with (keys, map)
   Handle<MapCache> AddToMapCache(Handle<Context> context,
                                  Handle<FixedArray> keys,
                                  Handle<Map> map);
 
   // Attempt to find the number in a small cache.  If we finds it, return
   // 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_