Adds tests for NPB Mac UNNotification

This adds tests for the different methods in the bridge, and the
different scenarios that can happen when displaying a notification. It
also tests features specific to the API.

Change-Id: Id58fe2a63c19baf2b1cb6a83cc488d3c060692cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2517466Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Richard Knoll <knollr@chromium.org>
Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Commit-Queue: Mohamed Adel <adelm@google.com>
Cr-Commit-Position: refs/heads/master@{#825848}

chrome/browser/ui/cocoa/notifications/unnotification_builder_mac_unittest.mm

@@ -32,6 +32,7 @@ base::scoped_nsobject<UNNotificationBuilder> NewTestBuilder(
   [builder setProfileId:@"profileId"];
   [builder setIncognito:false];
   [builder setCreatorPid:@1];
+  [builder setShowSettingsButton:NO];
   [builder setNotificationType:[NSNumber numberWithInt:static_cast<int>(type)]];
   return builder;
 }

chrome/test/BUILD.gn

@@ -3908,6 +3908,7 @@ test("unit_tests") {
       "../browser/mac/exception_processor_unittest.mm",
       "../browser/mac/keystone_glue_unittest.mm",
       "../browser/notifications/notification_platform_bridge_mac_unittest.mm",
+      "../browser/notifications/notification_platform_bridge_mac_unnotification_unittest.mm",
       "../browser/notifications/notification_platform_bridge_mac_utils_unittest.mm",
       "../browser/notifications/stub_alert_dispatcher_mac.h",
       "../browser/notifications/stub_alert_dispatcher_mac.mm",