Don't display a settings gear on non-MD extension notifications

Inline settings work fine for the MD notifications, but the handler
doesn't implement OpenSettings() for non-MD notifications, nor has
something sensible to do there. Instead, don't display the button.

Bug: 828346
Change-Id: I3a57f940be773e40e4994e4e6e1920f0c83ca3ec
Reviewed-on: https://chromium-review.googlesource.com/1002812Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549207}

chrome/browser/extensions/api/notifications/notifications_api.cc

@@ -361,7 +361,7 @@ bool NotificationsApiFunction::CreateNotification(
   optional_fields.settings_button_handler =
       base::FeatureList::IsEnabled(message_center::kNewStyleNotifications)
           ? message_center::SettingsButtonHandler::INLINE
-          : message_center::SettingsButtonHandler::DELEGATE;
+          : message_center::SettingsButtonHandler::NONE;
 
   // TODO(crbug.com/772004): Remove the manual limitation in favor of an IDL
   // annotation once supported.