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

extensions/shell/browser/shell_display_info_provider.cc

 // 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.
 
 #include "extensions/shell/browser/shell_display_info_provider.h"
 
 namespace extensions {
 
 ShellDisplayInfoProvider::ShellDisplayInfoProvider() {
 }
@@ skipping 12 matching lines @@
 void ShellDisplayInfoProvider::UpdateDisplayUnitInfoForPlatform(
     const gfx::Display& display,
     extensions::api::system_display::DisplayUnitInfo* unit) {
   static bool logged_once = false;
   if (!logged_once) {
     NOTIMPLEMENTED();
     logged_once = true;
   }
 }
 
-gfx::Screen* ShellDisplayInfoProvider::GetActiveScreen() {
-  return NULL;
-}
-
 // static
 DisplayInfoProvider* DisplayInfoProvider::Create() {
   return new ShellDisplayInfoProvider();
 }
 
 }  // namespace extensions