Revert of Implement a runtime headless mode for Linux

headless/lib/browser/headless_platform_event_source.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_LIB_BROWSER_HEADLESS_PLATFORM_EVENT_SOURCE_H_
-#define HEADLESS_LIB_BROWSER_HEADLESS_PLATFORM_EVENT_SOURCE_H_
-
-#include "base/macros.h"
-#include "ui/events/platform/platform_event_source.h"
-
-namespace headless {
-
-// A stub event source whose main purpose is to prevent the default platform
-// event source from getting created.
-class HeadlessPlatformEventSource : public ui::PlatformEventSource {
- public:
-  HeadlessPlatformEventSource();
-  ~HeadlessPlatformEventSource() override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(HeadlessPlatformEventSource);
-};
-
-}  // namespace headless
-
-#endif  // HEADLESS_LIB_BROWSER_HEADLESS_PLATFORM_EVENT_SOURCE_H_