Throw as per spec when modifying an Array with builtin methods

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 77dcb8cc818b985a43bb98fc8cea61392f93d6a9..fae9d94cb8f3488b97d5a4b7014ebe6ab88f5de0 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -10184,10 +10184,13 @@ class JSArray: public JSObject {
                                            uint32_t index,
                                            Handle<Object> value);
 
-  static bool IsReadOnlyLengthDescriptor(Handle<Map> jsarray_map);
+  static bool HasReadOnlyLength(Handle<JSArray> array);
   static bool WouldChangeReadOnlyLength(Handle<JSArray> array, uint32_t index);
   static MaybeHandle<Object> ReadOnlyLengthError(Handle<JSArray> array);
 
+  // TODO(adamk): Remove this method in favor of HasReadOnlyLength().
+  static bool IsReadOnlyLengthDescriptor(Handle<Map> jsarray_map);
+
   // Initialize the array with the given capacity. The function may
   // fail due to out-of-memory situations, but only if the requested
   // capacity is non-zero.