Keep function.prototype fast.

src/factory.cc

 // 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.
 
 #include "src/factory.h"
 
 #include "src/allocation-site-scopes.h"
 #include "src/conversions.h"
 #include "src/isolate-inl.h"
 #include "src/macro-assembler.h"
@@ skipping 1300 matching lines @@
   Handle<Map> new_map;
   if (function->shared()->is_generator()) {
     // Generator prototypes can share maps since they don't have "constructor"
     // properties.
     new_map = handle(native_context->generator_object_prototype_map());
   } else {
     // Each function prototype gets a fresh map to avoid unwanted sharing of
     // maps between prototypes of different constructors.
     Handle<JSFunction> object_function(native_context->object_function());
     ASSERT(object_function->has_initial_map());
-    new_map = Map::Copy(handle(object_function->initial_map()));
+    new_map = Map::CopyAsPrototypeMap(handle(object_function->initial_map()));
   }
 
   Handle<JSObject> prototype = NewJSObjectFromMap(new_map);
 
   if (!function->shared()->is_generator()) {
     JSObject::AddProperty(prototype, constructor_string(), function, DONT_ENUM);
   }
 
   return prototype;
 }
@@ skipping 1033 matching lines @@
   return Handle<Object>::null();
 }
 
 
 Handle<Object> Factory::ToBoolean(bool value) {
   return value ? true_value() : false_value();
 }
 
 
 } }  // namespace v8::internal