[elements] Precisely estimate elements size for large-object limits

src/elements.h

Index: src/elements.h
diff --git a/src/elements.h b/src/elements.h
index 9f70f2a0c753864e72ddb5f84754304a42ddfa8a..b5fe6dbdef382539b1722a54634c2e420977e293 100644
--- a/src/elements.h
+++ b/src/elements.h
@@ -56,6 +56,7 @@ class ElementsAccessor {
 
   virtual PropertyDetails GetDetails(JSObject* holder, uint32_t entry) = 0;
   virtual bool HasAccessors(JSObject* holder) = 0;
+  virtual uint32_t NumberOfElements(JSObject* holder) = 0;
 
   // Modifies the length data property as specified for JSArrays and resizes the
   // underlying backing store accordingly. The method honors the semantics of
@@ -163,7 +164,7 @@ class ElementsAccessor {
   // indices are equivalent to entries. In the NumberDictionary
   // ElementsAccessor, entries are mapped to an index using the KeyAt method on
   // the NumberDictionary.
-  virtual uint32_t GetEntryForIndex(JSObject* holder,
+  virtual uint32_t GetEntryForIndex(Isolate* isolate, JSObject* holder,
                                     FixedArrayBase* backing_store,
                                     uint32_t index) = 0;