Mojo C++ bindings: make the generator use STL/WTF string/vector/map by default.

chrome/browser/ui/webui/engagement/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: chrome/chrome_web_ui_mojo_bindings.gyp:webui_mojo_bindings
 mojom("mojo_bindings") {
   sources = [
     "site_engagement.mojom",
   ]
 
   public_deps = [
     "//url/mojo:url_mojom_gurl",
   ]
+
+  use_new_wrapper_types = false
 }