Remove remainder of Athena related code from Chrome

chrome/browser/extensions/display_info_provider_athena.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_EXTENSIONS_DISPLAY_INFO_PROVIDER_ATHENA_H_
-#define CHROME_BROWSER_EXTENSIONS_DISPLAY_INFO_PROVIDER_ATHENA_H_
-
-#include "extensions/browser/api/system_display/display_info_provider.h"
-
-namespace extensions {
-
-// TODO: Merge into DisplayInfoProviderChromeOS once DisplayManager is
-// refactored. crbug.com/416961
-class DisplayInfoProviderAthena : public DisplayInfoProvider {
- public:
-  DisplayInfoProviderAthena();
-  virtual ~DisplayInfoProviderAthena();
-
-  // DisplayInfoProvider implementation.
-  virtual bool SetInfo(const std::string& display_id,
-                       const core_api::system_display::DisplayProperties& info,
-                       std::string* error) override;
-  virtual void UpdateDisplayUnitInfoForPlatform(
-      const gfx::Display& display,
-      core_api::system_display::DisplayUnitInfo* unit) override;
-  virtual gfx::Screen* GetActiveScreen() override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(DisplayInfoProviderAthena);
-};
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_EXTENSIONS_DISPLAY_INFO_PROVIDER_ATHENA_H_