Add a basic demo mode browser test.

chrome/browser/chromeos/login/test/app_window_waiter.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_TEST_APP_WINDOW_WAITER_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_TEST_APP_WINDOW_WAITER_H_
+
+#include <string>
+
+#include "apps/app_window_registry.h"
+#include "base/basictypes.h"
+#include "base/run_loop.h"
+
+namespace apps {
+class AppWindow;
+}
+
+namespace chromeos {
+
+// Helper class that monitors app windows to wait for a window to appear.
+class AppWindowWaiter : public apps::AppWindowRegistry::Observer {
+ public:
+  AppWindowWaiter(apps::AppWindowRegistry* registry,
+                  const std::string& app_id);
+  virtual ~AppWindowWaiter();
+
+  apps::AppWindow* Wait();

[bartfab (slow), 2014/03/27 14:13:29]

Nit: RunLoop::Run() can only be called once per RunLoop lifetime. This implies
that your Wait() method can only be called once per AppWindowWaiter lifetime.
That should be documented.

[rkc, 2014/03/27 21:43:10]

Done.

+
+  // AppWindowRegistry::Observer:
+  virtual void OnAppWindowAdded(apps::AppWindow* app_window) OVERRIDE;

[bartfab (slow), 2014/03/27 14:13:29]

Nit: #include "base/compiler_specific.h"

[rkc, 2014/03/27 21:43:10]

Done.

+  virtual void OnAppWindowIconChanged(apps::AppWindow* app_window) OVERRIDE;
+  virtual void OnAppWindowRemoved(apps::AppWindow* app_window) OVERRIDE;
+
+ private:
+  apps::AppWindowRegistry* registry_;
+  std::string app_id_;
+  base::RunLoop run_loop_;
+  apps::AppWindow* window_;
+
+  DISALLOW_COPY_AND_ASSIGN(AppWindowWaiter);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_TEST_APP_WINDOW_WAITER_H_