Move CallSite.toString to C++

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 181c20052734e217138906ee13d72c53a2e8c613..ebf1812a4e8ce5381ba87c27958c372e38e51b1d 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2671,7 +2671,8 @@ void Bootstrapper::ExportFromRuntime(Isolate* isolate,
           {"isConstructor", Builtins::kCallSitePrototypeIsConstructor},
           {"isEval", Builtins::kCallSitePrototypeIsEval},
           {"isNative", Builtins::kCallSitePrototypeIsNative},
-          {"isToplevel", Builtins::kCallSitePrototypeIsToplevel}};
+          {"isToplevel", Builtins::kCallSitePrototypeIsToplevel},
+          {"toString", Builtins::kCallSitePrototypeToString}};
 
       PropertyAttributes attrs =
           static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);