[runtime] Rewrite Function.prototype.toString in C++.

src/elements.cc

Index: src/elements.cc
diff --git a/src/elements.cc b/src/elements.cc
index 28700b8f0abe31e90e32a0f2c6be65d787c915dd..96aeb645f34fef6dce4887f7bed6aa695be5c1cf 100644
--- a/src/elements.cc
+++ b/src/elements.cc
@@ -428,8 +428,8 @@ static void TraceTopFrame(Isolate* isolate) {
   }
   StackFrame* raw_frame = it.frame();
   if (raw_frame->is_internal()) {
-    Code* apply_builtin = isolate->builtins()->builtin(
-        Builtins::kFunctionApply);
+    Code* apply_builtin =
+        isolate->builtins()->builtin(Builtins::kFunctionPrototypeApply);
     if (raw_frame->unchecked_code() == apply_builtin) {
       PrintF("apply from ");
       it.Advance();