Merge AddFastElement and AddFastDoubleElement

src/elements.h

Index: src/elements.h
diff --git a/src/elements.h b/src/elements.h
index 1f36495e98047862dbca7e9e4ecfcb49a0ef20a3..bab02b86dec5eb730aae67fac3f52f9f702041c8 100644
--- a/src/elements.h
+++ b/src/elements.h
@@ -138,6 +138,9 @@ class ElementsAccessor {
   static void InitializeOncePerProcess();
   static void TearDown();
 
+  virtual void Set(FixedArrayBase* backing_store, uint32_t key,
+                   Object* value) = 0;
+
  protected:
   friend class SloppyArgumentsElementsAccessor;
   friend class LookupIterator;
@@ -164,9 +167,6 @@ class ElementsAccessor {
                                      uint32_t index) = 0;
   virtual bool HasIndex(FixedArrayBase* backing_store, uint32_t key) = 0;
 
-  virtual void Set(FixedArrayBase* backing_store, uint32_t key,
-                   Object* value) = 0;
-
  private:
   static ElementsAccessor** elements_accessors_;
   const char* name_;