[builtins] Move StringLastIndexOf to a builtin.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 249513c93bf334f8348a0e217bb98324075d021c..5afcdc4736acde850ff7bfb95144a9c8beb874ac 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -9251,6 +9251,9 @@ class String: public Name {
   static int IndexOf(Isolate* isolate, Handle<String> sub, Handle<String> pat,
                      int start_index);
 
+  static Object* LastIndexOf(Isolate* isolate, Handle<Object> receiver,
+                             Handle<Object> search, Handle<Object> position);
+
   // String equality operations.
   inline bool Equals(String* other);
   inline static bool Equals(Handle<String> one, Handle<String> two);