Remove kDisableDownloadNotification and stop compiling shelf code on

chrome/browser/download/notification/download_notification_manager.cc

 // Copyright 2015 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/download/notification/download_notification_manager.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/download/download_item_model.h"
 #include "chrome/browser/download/notification/download_item_notification.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/grit/chromium_strings.h"
 #include "content/public/browser/download_item.h"
 #include "grit/theme_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_delegate.h"
 
 ///////////////////////////////////////////////////////////////////////////////
 // DownloadNotificationManager implementation:
 ///////////////////////////////////////////////////////////////////////////////
 
-bool DownloadNotificationManager::IsEnabled() {
-  return !base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kDisableDownloadNotification);
-}
-
 DownloadNotificationManager::DownloadNotificationManager(Profile* profile)
     : main_profile_(profile),
       items_deleter_(&manager_for_profile_) {
 }
 
 DownloadNotificationManager::~DownloadNotificationManager() {
 }
 
 void DownloadNotificationManager::OnAllDownloadsRemoving(Profile* profile) {
   DownloadNotificationManagerForProfile* manager_for_profile =
@@ skipping 104 matching lines @@
 
   DownloadItemNotification* item = new DownloadItemNotification(download, this);
   items_.insert(std::make_pair(download, item));
 }
 
 void DownloadNotificationManagerForProfile::OverrideMessageCenterForTest(
     message_center::MessageCenter* message_center) {
   DCHECK(message_center);
   message_center_ = message_center;
 }