Restructuring of JSObject::preventExtensions.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 2f1405f57d10825a38899967a80d41ffca23d5cd..1c6e6e9c5760598b738e970dc7ee81fe0cc06a26 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2267,9 +2267,11 @@ class JSObject: public JSReceiver {
   // Check whether this object references another object
   bool ReferencesObject(Object* obj);
 
-  // Disalow further properties to be added to the oject.
+  // Disallow further properties to be added to the oject.
+  MUST_USE_RESULT static Maybe<bool> PreventExtensionsInternal(
+      Handle<JSObject> object);  // ES [[PreventExtensions]]
   MUST_USE_RESULT static MaybeHandle<Object> PreventExtensions(
-      Handle<JSObject> object);
+      Handle<JSObject> object);  // ES Object.preventExtensions
 
   static bool IsExtensible(Handle<JSObject> object);
 
@@ -2461,7 +2463,7 @@ class JSObject: public JSReceiver {
   // Helper for fast versions of preventExtensions, seal, and freeze.
   // attrs is one of NONE, SEALED, or FROZEN (depending on the operation).
   template <PropertyAttributes attrs>
-  MUST_USE_RESULT static MaybeHandle<Object> PreventExtensionsWithTransition(
+  MUST_USE_RESULT static Maybe<bool> PreventExtensionsWithTransition(
       Handle<JSObject> object);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSObject);