Add possibility to configure 'prototype' property via FunctionTemplate

src/apinatives.js

Index: src/apinatives.js
diff --git a/src/apinatives.js b/src/apinatives.js
index ca2bbf5c5355c53bb39ab249c7941adf284a6a39..193863f5c2f9f99cccb42432b0b6902b47898aff 100644
--- a/src/apinatives.js
+++ b/src/apinatives.js
@@ -73,7 +73,15 @@ function InstantiateFunction(data, name) {
       if (name) %FunctionSetName(fun, name);
       cache[serialNumber] = fun;
       var prototype = %GetTemplateField(data, kApiPrototypeTemplateOffset);
-      fun.prototype = prototype ? Instantiate(prototype) : {};
+      var attributes = %GetTemplateField(data, kApiPrototypeAttributesOffset);
+      if (attributes != NONE) {
+        %IgnoreAttributesAndSetProperty(
+            fun, "prototype",
+            prototype ? Instantiate(prototype) : {},
+            attributes);
+      } else {
+        fun.prototype = prototype ? Instantiate(prototype) : {};
+      }
       %SetProperty(fun.prototype, "constructor", fun, DONT_ENUM);
       var parent = %GetTemplateField(data, kApiParentTemplateOffset);
       if (parent) {