[regexp] Port RegExpConstructResultStub to TurboFan

src/runtime/runtime-regexp.cc

Index: src/runtime/runtime-regexp.cc
diff --git a/src/runtime/runtime-regexp.cc b/src/runtime/runtime-regexp.cc
index b36e5e66cbae17b447958a05c6ef192a94197272..977e6bc48f82a637ff7df18e41cfc055d1829a3c 100644
--- a/src/runtime/runtime-regexp.cc
+++ b/src/runtime/runtime-regexp.cc
@@ -794,7 +794,7 @@ RUNTIME_FUNCTION(Runtime_RegExpSource) {
   return regexp->source();
 }
 
-
+// TODO(jgruber): Remove this once all uses in regexp.js have been removed.
 RUNTIME_FUNCTION(Runtime_RegExpConstructResult) {
   HandleScope handle_scope(isolate);
   DCHECK(args.length() == 3);