test: ensure `sender-pid` hint is set in Linux notifications (#43928)

test: expect a `sender-pid` hint in Linux notifications.

This PR ensures that the `sender-pid` hint is set for new notifications.
It also updates the spec to confirm that DBus receives the hint and that
it has the correct value.

This fixes a spec failure when running libnotify >= 0.7.12 (2022-05-05).
Starting with that version, libnotify started injecting `sender-pid` if
not provided by the client. So our tests received a slightly different
DBus payload depending on what version of libnotify was installed,
causing our deep-equals tests to fail.

By always providing and testing the `sender-pid` hint, our behavior and
tests should be consistent across distros.

BUILD.gn

@@ -75,6 +75,7 @@ if (is_linux) {
       "notify_notification_set_timeout",
       "notify_notification_set_urgency",
       "notify_notification_set_hint_string",
+      "notify_notification_set_hint",
       "notify_notification_show",
       "notify_notification_close",
     ]

shell/browser/notifications/linux/libnotify_notification.cc

@@ -10,6 +10,7 @@
 #include "base/files/file_enumerator.h"
 #include "base/functional/bind.h"
 #include "base/logging.h"
+#include "base/process/process_handle.h"
 #include "base/strings/utf_string_conversions.h"
 #include "shell/browser/notifications/notification_delegate.h"
 #include "shell/browser/ui/gtk_util.h"
@@ -145,6 +146,10 @@ void LibnotifyNotification::Show(const NotificationOptions& options) {
         notification_, "desktop-entry", desktop_id.c_str());
   }
 
+  libnotify_loader_.notify_notification_set_hint(
+      notification_, "sender-pid",
+      g_variant_new_int64(base::GetCurrentProcId()));
+
   GError* error = nullptr;
   libnotify_loader_.notify_notification_show(notification_, &error);
   if (error) {

spec/api-notification-dbus-spec.ts

@@ -124,6 +124,7 @@ ifdescribe(!skip)('Notification module (dbus)', () => {
           append: 'true',
           image_data: [3, 3, 12, true, 8, 4, Buffer.from([255, 0, 0, 255, 0, 0, 0, 255, 0, 0, 0, 0, 76, 255, 0, 255, 0, 0, 0, 255, 0, 0, 0, 0, 0, 38, 255, 255, 0, 0, 0, 255, 0, 0, 0, 0])],
           'desktop-entry': appName,
+          'sender-pid': process.pid,
           urgency: 1
         }
       });