Move enable extensions define to a build flag.

chrome/browser/download/download_service_impl.h

 // 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.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_SERVICE_IMPL_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_SERVICE_IMPL_H_
 
 #include <memory>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "chrome/browser/download/download_service.h"
 #include "components/keyed_service/core/keyed_service.h"
+#include "extensions/features/features.h"
 
 class ChromeDownloadManagerDelegate;
 class DownloadHistory;
 class DownloadUIController;
 class ExtensionDownloadsEventRouter;
 class Profile;
 
 namespace content {
 class DownloadManager;
 }
 
 namespace extensions {
 class ExtensionDownloadsEventRouter;
 }
 
 // Owning class for ChromeDownloadManagerDelegate.
 class DownloadServiceImpl : public DownloadService {
  public:
   explicit DownloadServiceImpl(Profile* profile);
   ~DownloadServiceImpl() override;
 
   // DownloadService
   ChromeDownloadManagerDelegate* GetDownloadManagerDelegate() override;
   DownloadHistory* GetDownloadHistory() override;
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   extensions::ExtensionDownloadsEventRouter* GetExtensionEventRouter() override;
 #endif
   bool HasCreatedDownloadManager() override;
   int NonMaliciousDownloadCount() const override;
   void CancelDownloads() override;
   void SetDownloadManagerDelegateForTesting(
       std::unique_ptr<ChromeDownloadManagerDelegate> delegate) override;
   bool IsShelfEnabled() override;
 
   // KeyedService
@@ skipping 14 matching lines @@
   // notifying the UI of any new downloads. Its lifetime matches that of the
   // associated download manager.
   // Note on destruction order: download_ui_ depends on download_history_ and
   // should be destroyed before the latter.
   std::unique_ptr<DownloadUIController> download_ui_;
 
 // On Android, GET downloads are not handled by the DownloadManager.
 // Once we have extensions on android, we probably need the EventRouter
 // in ContentViewDownloadDelegate which knows about both GET and POST
 // downloads.
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // The ExtensionDownloadsEventRouter dispatches download creation, change, and
   // erase events to extensions. Like ChromeDownloadManagerDelegate, it's a
   // chrome-level concept and its lifetime should match DownloadManager. There
   // should be a separate EDER for on-record and off-record managers.
   // There does not appear to be a separate ExtensionSystem for on-record and
   // off-record profiles, so ExtensionSystem cannot own the EDER.
   std::unique_ptr<extensions::ExtensionDownloadsEventRouter>
       extension_event_router_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DownloadServiceImpl);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_SERVICE_IMPL_H_