Revert of Remove GetAttributes from the mix to avoid another virtual dispatch.

src/elements.h

Index: src/elements.h
diff --git a/src/elements.h b/src/elements.h
index 310891ab1e030be14f8413dcef21680f4471a2cd..60ff130d2998ce59089567e218ee2716de6cae9b 100644
--- a/src/elements.h
+++ b/src/elements.h
@@ -58,6 +58,19 @@
 
   inline Handle<Object> Get(Handle<JSObject> holder, uint32_t key) {
     return Get(holder, key, handle(holder->elements()));
+  }
+
+  // Returns an element's attributes, or ABSENT if there is no such
+  // element. This method doesn't iterate up the prototype chain.  The caller
+  // can optionally pass in the backing store to use for the check, which must
+  // be compatible with the ElementsKind of the ElementsAccessor. If
+  // backing_store is NULL, the holder->elements() is used as the backing store.
+  virtual PropertyAttributes GetAttributes(JSObject* holder, uint32_t key,
+                                           FixedArrayBase* backing_store) = 0;
+
+  inline PropertyAttributes GetAttributes(Handle<JSObject> holder,
+                                          uint32_t key) {
+    return GetAttributes(*holder, key, holder->elements());
   }
 
   // Returns an element's accessors, or NULL if the element does not exist or
@@ -173,8 +186,7 @@
   // the index to a key using the KeyAt method on the NumberDictionary.
   virtual uint32_t GetKeyForIndex(FixedArrayBase* backing_store,
                                   uint32_t index) = 0;
-  virtual uint32_t GetIndexForKey(JSObject* holder,
-                                  FixedArrayBase* backing_store,
+  virtual uint32_t GetIndexForKey(FixedArrayBase* backing_store,
                                   uint32_t key) = 0;
   virtual PropertyDetails GetDetails(FixedArrayBase* backing_store,
                                      uint32_t index) = 0;