headless: Librarify Headless Shell

headless/public/headless_shell.h

+// 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 HEADLESS_PUBLIC_HEADLESS_SHELL_H_
+#define HEADLESS_PUBLIC_HEADLESS_SHELL_H_
+
+#include "headless/public/headless_export.h"
+
+namespace headless {
+
+// Start the Headless Shell application. Intended to be called early in main().
+// Returns the exit code for the process.
+int HEADLESS_EXPORT HeadlessShellMain(int argc, const char** argv);
+
+}  // namespace headless
+
+#endif  // HEADLESS_PUBLIC_HEADLESS_SHELL_H_