Remove now-unnecessary wrappers around gfx::Screen::GetScreen()

chrome/browser/extensions/display_info_provider_chromeos.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_CHROMEOS_H_
 #define CHROME_BROWSER_EXTENSIONS_DISPLAY_INFO_PROVIDER_CHROMEOS_H_
 
 #include "base/macros.h"
 #include "extensions/browser/api/system_display/display_info_provider.h"
 
 namespace extensions {
 
 class DisplayInfoProviderChromeOS : public DisplayInfoProvider {
  public:
   DisplayInfoProviderChromeOS();
   ~DisplayInfoProviderChromeOS() override;
 
   // DisplayInfoProvider implementation.
   bool SetInfo(const std::string& display_id,
                const api::system_display::DisplayProperties& info,
                std::string* error) override;
   void UpdateDisplayUnitInfoForPlatform(
       const gfx::Display& display,
       api::system_display::DisplayUnitInfo* unit) override;
-  gfx::Screen* GetActiveScreen() override;
   void EnableUnifiedDesktop(bool enable) override;
   DisplayInfo GetAllDisplaysInfo() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DisplayInfoProviderChromeOS);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_DISPLAY_INFO_PROVIDER_CHROMEOS_H_