Remove remainder of Athena related code from Chrome

chrome/browser/extensions/display_info_provider_athena.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 "chrome/browser/extensions/display_info_provider_athena.h"
-
-namespace extensions {
-
-DisplayInfoProviderAthena::DisplayInfoProviderAthena() {
-}
-
-DisplayInfoProviderAthena::~DisplayInfoProviderAthena() {
-}
-
-bool DisplayInfoProviderAthena::SetInfo(
-    const std::string& display_id_str,
-    const core_api::system_display::DisplayProperties& info,
-    std::string* error) {
-  *error = "Not implemented";
-  return false;
-}
-
-void DisplayInfoProviderAthena::UpdateDisplayUnitInfoForPlatform(
-    const gfx::Display& display,
-    extensions::core_api::system_display::DisplayUnitInfo* unit) {
-  static bool logged_once = false;
-  if (!logged_once) {
-    NOTIMPLEMENTED();
-    logged_once = true;
-  }
-}
-
-gfx::Screen* DisplayInfoProviderAthena::GetActiveScreen() {
-  NOTIMPLEMENTED();
-  return NULL;
-}
-
-// static
-DisplayInfoProvider* DisplayInfoProvider::Create() {
-  return new DisplayInfoProviderAthena();
-}
-
-}  // namespace extensions