Get rid of KeepAlive. Quit shell when all urls run directly by Context are closed.

mojo/shell/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/public/tools/bindings/mojom.gni")
 import("//build/config/ui.gni")
 
 executable("mojo_shell") {
   deps = [
     ":lib",
@@ skipping 51 matching lines @@
     "context.h",
     "dbus_application_loader_linux.cc",
     "dbus_application_loader_linux.h",
     "dynamic_application_loader.cc",
     "dynamic_application_loader.h",
     "dynamic_service_runner.h",
     "init.cc",
     "init.h",
     "in_process_dynamic_service_runner.cc",
     "in_process_dynamic_service_runner.h",
-    "keep_alive.cc",
-    "keep_alive.h",
     "mojo_url_resolver.cc",
     "mojo_url_resolver.h",
     "out_of_process_dynamic_service_runner.cc",
     "out_of_process_dynamic_service_runner.h",
-    "run.cc",
-    "run.h",
     "switches.cc",
     "switches.h",
     "task_runners.cc",
     "task_runners.h",
     "test_child_process.cc",
     "test_child_process.h",
     "ui_application_loader_android.cc",
     "ui_application_loader_android.h",
   ]
 
@@ skipping 84 matching lines @@
 
   deps = [
     ":lib",
     "//base",
     "//base:base_static",
     "//mojo/application_manager",
     "//mojo/system",
     "//url",
   ]
 }