Add initial support for native Linux desktop notifications

chrome/browser/notifications/notification_display_service_factory.cc

 // Copyright 2016 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/notifications/notification_display_service_factory.h"
 
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/notifications/message_center_display_service.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_features.h"
+#include "chrome/common/features.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 
-#if defined(OS_ANDROID) || defined(OS_MACOSX)
+#if BUILDFLAG(ENABLE_NATIVE_NOTIFICATIONS)
 #include "chrome/browser/notifications/native_notification_display_service.h"
 #endif
 
 // static
 NotificationDisplayService* NotificationDisplayServiceFactory::GetForProfile(
     Profile* profile) {
   return static_cast<NotificationDisplayService*>(
       GetInstance()->GetServiceForBrowserContext(profile, true /* create */));
 }
 
 // static
 NotificationDisplayServiceFactory*
 NotificationDisplayServiceFactory::GetInstance() {
   return base::Singleton<NotificationDisplayServiceFactory>::get();
 }
 
 NotificationDisplayServiceFactory::NotificationDisplayServiceFactory()
     : BrowserContextKeyedServiceFactory(
           "NotificationDisplayService",
           BrowserContextDependencyManager::GetInstance()) {}
 
 // Selection of the implementation works as follows:
 //   - Android always uses the NativeNotificationDisplayService.
 //   - Mac uses the MessageCenterDisplayService by default, but can use the
 //     NativeNotificationDisplayService by using the chrome://flags or via
 //     the --enable-features=NativeNotifications command line flag.
 //   - All other platforms always use the MessageCenterDisplayService.
 KeyedService* NotificationDisplayServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
+#if BUILDFLAG(ENABLE_NATIVE_NOTIFICATIONS)
 #if defined(OS_ANDROID)
   return new NativeNotificationDisplayService(
       Profile::FromBrowserContext(context),
       g_browser_process->notification_platform_bridge());
-#elif defined(OS_MACOSX)
-  if (base::FeatureList::IsEnabled(features::kNativeNotifications)) {
+#else   // defined(OS_ANDROID)
+  if (base::FeatureList::IsEnabled(features::kNativeNotifications) &&
+      g_browser_process->notification_platform_bridge()) {
     return new NativeNotificationDisplayService(
         Profile::FromBrowserContext(context),
         g_browser_process->notification_platform_bridge());
   }
-#endif
+#endif  // defined(OS_ANDROID)
+#endif  // BUILDFLAG(ENABLE_NATIVE_NOTIFICATIONS)
   return new MessageCenterDisplayService(
       Profile::FromBrowserContext(context),
       g_browser_process->notification_ui_manager());
 }
 
 content::BrowserContext*
 NotificationDisplayServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextOwnInstanceInIncognito(context);
 }