Add chrome/browser/apps/BUILD.gn and move Chrome-specific code there

apps/DEPS

 include_rules = [
   "+base",
   "+cc/paint",
   "+content/public/app",
   "+content/public/browser",
   "+content/public/common",
   "+content/public/test",
   "+components/keyed_service",
   "+components/pref_registry/pref_registry_syncable.h",
   "+components/sessions",
   "+components/user_manager",
   "+components/web_modal",
   "+extensions",
   "+net/base",
   "+skia/ext",
   "+third_party/skia/include",
   "+ui",
   "+win8",
 
-  # Temporary allowed includes.
-  # TODO(benwells): remove these (http://crbug.com/159366)
-  "+chrome/browser/chrome_notification_types.h",
-  "+chrome/browser/chromeos/login/users/user_manager.h",
-  "+chrome/browser/lifetime/application_lifetime.h",
-  "+chrome/common/chrome_switches.h",
-
   # For default app icon.
   "!chrome/grit/theme_resources.h",
-
-  # Pieces of the extensions system that need to move to src/extensions.
-  # See http://crbug.com/162530 for details.
-  "+chrome/browser/extensions/api/file_system/file_system_api.h",
-  "+chrome/browser/extensions/chrome_extension_web_contents_observer.h",
-  "+chrome/browser/extensions/unpacked_installer.h",
 ]
 
 specific_include_rules = {
   # Needs to be able to reload extensions. http://crbug.com/162530
   "app_load_service\.cc": [
     "+chrome/browser/extensions/extension_service.h",
   ],
   "(.*test\.cc|.*test_mac\.mm)": [
     "+chrome/browser/browser_shutdown.h",
     "+chrome/browser/extensions/extension_browsertest.h",
     "+chrome/browser/extensions/extension_error_reporter.h",
     "+chrome/browser/extensions/extension_test_message_listener.h",
     "+chrome/browser/extensions/test_extension_environment.h",
     "+chrome/browser/profiles/profile_manager.h",
     "+chrome/browser/ui/browser.h",
     "+chrome/browser/ui/simple_message_box_internal.h",
+    "+chrome/common/chrome_switches.h",
     "+chrome/test/base/in_process_browser_test.h",
     "+chrome/test/base/interactive_test_utils.h",
     "+chrome/test/base/testing_profile.h",
     # Temporary allowed testing include.
     # TODO(benwells): Move app_browsertest_util into apps component once there
     # is an apps shell to test with.
     "+chrome/browser/apps/app_browsertest_util.h",
+    # Pieces of the extensions system that need to move to src/extensions.
+    # See http://crbug.com/162530 for details.
+    "+chrome/browser/extensions/api/file_system/file_system_api.h",
   ]
 }