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

chrome/browser/extensions/extension_system_impl.cc

Index: chrome/browser/extensions/extension_system_impl.cc
diff --git a/chrome/browser/extensions/extension_system_impl.cc b/chrome/browser/extensions/extension_system_impl.cc
index ddaf85214ebd97e6b17fb672e8e6977095387042..29c0f4167ac95a213b9c3469f1ee828a4b01cd9d 100644
--- a/chrome/browser/extensions/extension_system_impl.cc
+++ b/chrome/browser/extensions/extension_system_impl.cc
@@ -6,8 +6,6 @@
 
 #include <algorithm>
 
-#include "apps/app_restore_service.h"
-#include "apps/app_restore_service_factory.h"
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
@@ -17,6 +15,7 @@
 #include "base/strings/string_tokenizer.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
+#include "chrome/browser/apps/browser_context_keyed_service_factories.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/chrome_app_sorting.h"
@@ -335,9 +334,7 @@ void ExtensionSystemImpl::Shared::Observe(
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   DCHECK_EQ(chrome::NOTIFICATION_APP_TERMINATING, type);
-  CHECK(apps::AppRestoreServiceFactory::GetForBrowserContext(profile_));
-  apps::AppRestoreServiceFactory::GetForBrowserContext(profile_)
-      ->OnApplicationTerminating();
+  chrome_apps::NotifyApplicationTerminating(profile_);
 }
 
 //