[typedarrays] Implement %TypedArray%.prototype.lastIndexOf in C++

src/elements.h

Index: src/elements.h
diff --git a/src/elements.h b/src/elements.h
index 28635d5bead290dd37b9c4f03b30ac45316eafb9..d693092bfbea2ac3de3ed048a7d2e2a4d4cad25d 100644
--- a/src/elements.h
+++ b/src/elements.h
@@ -171,6 +171,11 @@ class ElementsAccessor {
                                       Handle<Object> value, uint32_t start,
                                       uint32_t length) = 0;
 
+  virtual Maybe<int64_t> LastIndexOfValue(Isolate* isolate,
+                                          Handle<JSObject> receiver,
+                                          Handle<Object> value,
+                                          uint32_t start) = 0;
+
   virtual void CopyElements(Handle<FixedArrayBase> source,
                             ElementsKind source_kind,
                             Handle<FixedArrayBase> destination, int size) = 0;