Don't compile download notification code on !CrOS.

chrome/chrome_browser.gypi

 # Copyright 2012 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.
 
 {
   'variables': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 896 matching lines @@
     # Cross-platform Aura files.
     'chrome_browser_aura_sources': [
       # This file is called _views but has aura calls in it.
       'browser/download/drag_download_item_views.cc',
       'browser/lifetime/application_lifetime_aura.cc',
       'browser/platform_util_aura.cc',
     ],
     # ChromeOS-sources not ending in _chromeos (which would be included in
     # other sections and filtered out for non-ChromeOS platforms.
     'chrome_browser_chromeos_sources': [
+      'browser/download/notification/download_item_notification.cc',
+      'browser/download/notification/download_item_notification.h',
+      'browser/download/notification/download_notification.cc',
+      'browser/download/notification/download_notification.h',
+      'browser/download/notification/download_notification_manager.cc',
+      'browser/download/notification/download_notification_manager.h',
       'browser/media/protected_media_identifier_infobar_delegate.cc',
       'browser/media/protected_media_identifier_infobar_delegate.h',
       'browser/media/protected_media_identifier_permission_context.cc',
       'browser/media/protected_media_identifier_permission_context.h',
       'browser/media/protected_media_identifier_permission_context_factory.cc',
       'browser/media/protected_media_identifier_permission_context_factory.h',
       'browser/metrics/chromeos_metrics_provider.cc',
       'browser/metrics/chromeos_metrics_provider.h',
       'browser/metrics/perf/random_selector.cc',
       'browser/metrics/perf/random_selector.h',
@@ skipping 120 matching lines @@
       'browser/download/download_commands.cc',
       'browser/download/download_commands.h',
       'browser/download/download_crx_util.cc',
       'browser/download/download_crx_util.h',
       'browser/download/download_danger_prompt.cc',
       'browser/download/download_danger_prompt.h',
       'browser/download/download_shelf.cc',
       'browser/download/download_shelf.h',
       'browser/download/download_shelf_context_menu.cc',
       'browser/download/download_shelf_context_menu.h',
-      'browser/download/notification/download_item_notification.cc',
-      'browser/download/notification/download_item_notification.h',
-      'browser/download/notification/download_notification.cc',
-      'browser/download/notification/download_notification.h',
-      'browser/download/notification/download_notification_manager.cc',
-      'browser/download/notification/download_notification_manager.h',
       'browser/feedback/feedback_profile_observer.cc',
       'browser/feedback/feedback_profile_observer.h',
       'browser/feedback/show_feedback_page.cc',
       'browser/feedback/system_logs/about_system_logs_fetcher.cc',
       'browser/feedback/system_logs/about_system_logs_fetcher.h',
       'browser/feedback/system_logs/log_sources/chrome_internal_log_source.cc',
       'browser/feedback/system_logs/log_sources/chrome_internal_log_source.h',
       'browser/feedback/system_logs/log_sources/memory_details_log_source.cc',
       'browser/feedback/system_logs/log_sources/memory_details_log_source.h',
       'browser/feedback/system_logs/scrubbed_system_logs_fetcher.cc',
@@ skipping 3032 matching lines @@
             '../components/components.gyp:omnibox_browser',
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
           ],
         },
       ],
     }],
   ],
 }