Don't compile download notification code on !CrOS.

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() {
-#if defined(OS_CHROMEOS)
   bool enable_download_notification = true;
-#else
-  bool enable_download_notification = false;
-#endif
-
   std::string arg = base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
       switches::kEnableDownloadNotification);
   if (!arg.empty()) {
     if (arg == "enabled")
       enable_download_notification = true;
     else if (arg == "disabled")
       enable_download_notification = false;
   }
   return enable_download_notification;
 }
@@ skipping 103 matching lines @@
   DCHECK_EQ(profile_,
             Profile::FromBrowserContext(download->GetBrowserContext()));
 
   download->AddObserver(this);
 
   // |item| object will be inserted to |items_| by |OnCreated()| called in the
   // constructor.
   DownloadItemNotification* item = new DownloadItemNotification(download, this);
   items_.insert(std::make_pair(download, item));
 }