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

components/startup_metric_utils/common/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")
 
 source_set("common") {
   sources = [
     "pre_read_field_trial_utils_win.cc",
     "pre_read_field_trial_utils_win.h",
   ]
 
   deps = [
     "//base",
     "//components/variations",
     "//ipc",
   ]
 }
 
 mojom("interfaces") {
   sources = [
     "startup_metric.mojom",
   ]
   deps = [
     "//mojo/common:common_custom_types",
   ]
+
+  use_new_wrapper_types = false
 }