Make JSFunctionPrint() output Builtin names

This change has been useful when inspecting on_reject callbacks in
Isolate::InternalPromiseHasUserDefinedRejectHandler, it's probably
going to be helpful for other things too.

BUG=
R=adamk@chromium.org, littledan@chromium.org

Change-Id: I7c5bac87a3b8bd3ce19d71cf73397a93109976ba
Reviewed-on: https://chromium-review.googlesource.com/907641Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Cr-Commit-Position: refs/heads/master@{#51164}

src/objects-printer.cc

@@ -1107,6 +1107,21 @@ void JSFunction::JSFunctionPrint(std::ostream& os) {  // NOLINT
   }
   os << "\n - shared_info = " << Brief(shared());
   os << "\n - name = " << Brief(shared()->name());
+
+  // Print Builtin name for builtin functions
+  int builtin_index = code()->builtin_index();
+  if (builtin_index != -1 && !IsInterpreted()) {
+    if (builtin_index == Builtins::kDeserializeLazy) {
+      if (shared()->HasLazyDeserializationBuiltinId()) {
+        builtin_index = shared()->lazy_deserialization_builtin_id();
+        os << "\n - builtin: " << GetIsolate()->builtins()->name(builtin_index)
+           << "(lazy)";
+      }
+    } else {
+      os << "\n - builtin: " << GetIsolate()->builtins()->name(builtin_index);
+    }
+  }
+
   os << "\n - formal_parameter_count = "
      << shared()->internal_formal_parameter_count();
   os << "\n - kind = " << shared()->kind();