Make Function.length and Function.name configurable properties.

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5081 matching lines @@
 
   // Special case for callback properties.
   if (lookup.IsPropertyCallbacks()) {
     Handle<Object> callback(lookup.GetCallbackObject(), isolate);
     // To be compatible with Safari we do not change the value on API objects
     // in Object.defineProperty(). Firefox disagrees here, and actually changes
     // the value.
     if (callback->IsAccessorInfo()) {
       return isolate->heap()->undefined_value();
     }
-    // Avoid redefining foreign callback as data property, just use the stored
-    // setter to update the value instead.
+    // Provided a read-only property isn't being reconfigured, avoid redefining
+    // foreign callback as data property, just use the stored setter to update
+    // the value instead.
     // TODO(mstarzinger): So far this only works if property attributes don't
     // change, this should be fixed once we cleanup the underlying code.
-    if (callback->IsForeign() && lookup.GetAttributes() == attr) {
+    if (callback->IsForeign() &&
+        lookup.GetAttributes() == attr &&
+        !(attr & READ_ONLY)) {
       Handle<Object> result_object =
           JSObject::SetPropertyWithCallback(js_object,
                                             callback,
                                             name,
                                             obj_value,
                                             handle(lookup.holder()),
                                             kStrictMode);
       RETURN_IF_EMPTY_HANDLE(isolate, result_object);
       return *result_object;
     }
@@ skipping 9751 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal