Add a mojo::RunApplication() for running implementations of ApplicationImplBase.

mojo/public/cpp/application/BUILD.gn

 # Copyright 2014 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_sdk.gni")
 
 # GYP version: mojo/public/mojo_public.gyp:mojo_application_base
 mojo_sdk_source_set("application") {
   sources = [
     "application_delegate.h",
@@ skipping 14 matching lines @@
     "mojo/public/cpp/bindings",
     "mojo/public/cpp/environment",
     "mojo/public/cpp/system",
     "mojo/public/interfaces/application",
   ]
 }
 
 # GYP version: mojo/public/mojo_public.gyp:mojo_application_standalone
 mojo_sdk_source_set("standalone") {
   sources = [
+    "application_runner.h",
     "lib/application_runner.cc",
+    "lib/run_application.cc",
+    "run_application.h",
   ]
 
   public_deps = [
     ":application",
   ]
 
   mojo_sdk_deps = [
     "mojo/public/cpp/environment:standalone",
+    "mojo/public/cpp/system",
     "mojo/public/cpp/utility",
+    "mojo/public/interfaces/application",
   ]
 }
 
 mojo_sdk_source_set("test_support") {
   testonly = true
   sources = [
     "application_test_base.h",
     "lib/application_test_base.cc",
   ]
 
@@ skipping 25 matching lines @@
   ]
 
   mojo_sdk_deps = [
     "mojo/public/interfaces/application",
     "mojo/public/cpp/environment:standalone",
     "mojo/public/cpp/system",
     "mojo/public/cpp/utility",
     "mojo/public/interfaces/application",
   ]
 }