Add the first app_shell_browsertest test.

apps/test/app_shell_test.cc

-// 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.
-
-#include "apps/test/app_shell_test.h"
-
-#include "apps/shell/browser/shell_content_browser_client.h"
-#include "apps/shell/browser/shell_extension_system.h"
-#include "base/files/file_path.h"
-#include "base/logging.h"
-#include "extensions/browser/extension_system.h"
-
-namespace apps {
-
-AppShellTest::AppShellTest()
-    : browser_context_(NULL), extension_system_(NULL) {}
-
-AppShellTest::~AppShellTest() {}
-
-void AppShellTest::SetUpOnMainThread() {
-  browser_context_ = ShellContentBrowserClient::Get()->GetBrowserContext();
-
-  extension_system_ = static_cast<extensions::ShellExtensionSystem*>(
-      extensions::ExtensionSystem::Get(browser_context_));
-}
-
-void AppShellTest::RunTestOnMainThreadLoop() {
-  // Pump startup related events.
-  base::MessageLoopForUI::current()->RunUntilIdle();
-
-  SetUpOnMainThread();
-
-  RunTestOnMainThread();
-
-  TearDownOnMainThread();
-}
-
-bool AppShellTest::LoadAndLaunchApp(const base::FilePath& app_dir) {
-  return extension_system_->LoadAndLaunchApp(app_dir);
-}
-
-}  // namespace apps