[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 a4ae6854baf4f6256531cc5e6b11f07513bce1db..fc2e6a4fdbb09078c7fd2d383e44306e82a2cdf9 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
@@ -185,7 +186,7 @@ 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;