Adding ElementsAccessor::Concat

src/elements.h

Index: src/elements.h
diff --git a/src/elements.h b/src/elements.h
index e7a189008fda17be72987b6c50fe7481d0bb6565..bb8b439d727bd33bbc9a962fe718dd57e487ab71 100644
--- a/src/elements.h
+++ b/src/elements.h
@@ -127,8 +127,9 @@ class ElementsAccessor {
                    Handle<Object> value, PropertyAttributes attributes,
                    uint32_t new_capacity) = 0;
 
-  // TODO(cbruni): Consider passing Arguments* instead of Object** depending on
-  // the requirements of future callers.
+  static Handle<JSArray> Concat(Isolate* isolate, Arguments* args,
+                                uint32_t concat_size);
+
   virtual uint32_t Push(Handle<JSArray> receiver,
                         Handle<FixedArrayBase> backing_store, Arguments* args,
                         uint32_t push_size) = 0;