Empty Array prototype elements protection needs to alert on length change.

src/isolate.h

 // Copyright 2012 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_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <queue>
 #include "include/v8-debug.h"
 #include "src/allocation.h"
@@ skipping 1003 matching lines @@
 
   Map* get_initial_js_array_map(ElementsKind kind);
 
   bool IsFastArrayConstructorPrototypeChainIntact();
 
   // On intent to set an element in object, make sure that appropriate
   // notifications occur if the set is on the elements of the array or
   // object prototype. Also ensure that changes to prototype chain between
   // Array and Object fire notifications.
   void UpdateArrayProtectorOnSetElement(Handle<JSObject> object);
+  void UpdateArrayProtectorOnSetLength(Handle<JSObject> object) {
+    UpdateArrayProtectorOnSetElement(object);
+  }
   void UpdateArrayProtectorOnSetPrototype(Handle<JSObject> object) {
     UpdateArrayProtectorOnSetElement(object);
   }
   void UpdateArrayProtectorOnNormalizeElements(Handle<JSObject> object) {
     UpdateArrayProtectorOnSetElement(object);
   }
 
   // Returns true if array is the initial array prototype in any native context.
   bool IsAnyInitialArrayPrototype(Handle<JSArray> array);
 
@@ skipping 550 matching lines @@
   }
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ISOLATE_H_