Creates BackgroundShell and uses it in test

mojo/shell/background/background_shell.h

Index: mojo/shell/background/background_shell.h
diff --git a/mojo/shell/background/background_shell.h b/mojo/shell/background/background_shell.h
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+// Copyright 2016 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 MOJO_SHELL_BACKGROUND_BACKGROUND_SHELL_H_
+#define MOJO_SHELL_BACKGROUND_BACKGROUND_SHELL_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "mojo/shell/public/interfaces/application.mojom.h"
+
+class GURL;
+
+namespace mojo {
+namespace shell {
+
+// BackgroundShell starts up the mojo shell on a background thread, and
+// destroys the thread in the destructor. Once created use CreateApplication()
+// to obtain an InterfaceRequest for the Application. The InterfaceRequest can
+// then be bound to an ApplicationImpl.
+class BackgroundShell {
+ public:
+  BackgroundShell();
+  ~BackgroundShell();
+
+  void Init();
+
+  // Obtains an InterfaceRequest for the specified url.
+  InterfaceRequest<mojom::Application> CreateApplication(const GURL& url);
+
+ private:
+  class MojoThread;
+
+  scoped_ptr<MojoThread> thread_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackgroundShell);
+};
+
+}  // namespace shell
+}  // namespace mojo
+
+#endif  // MOJO_SHELL_BACKGROUND_BACKGROUND_SHELL_H_