gamepad: Return an invalid handle after ReportBadMessage

Bug: 1285449
Change-Id: I746c539577f7bdf69cbe4212ac380e0c92a5c771
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3373944
Auto-Submit: Matt Reynolds <mattreynolds@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#961125}

device/gamepad/gamepad_monitor.cc

@@ -53,6 +53,8 @@ void GamepadMonitor::GamepadStartPolling(GamepadStartPollingCallback callback) {
   GamepadService* service = GamepadService::GetInstance();
   if (!service->ConsumerBecameActive(this)) {
     mojo::ReportBadMessage("GamepadMonitor::GamepadStartPolling failed");
+    std::move(callback).Run(base::ReadOnlySharedMemoryRegion());
+    return;
   }
   std::move(callback).Run(service->DuplicateSharedMemoryRegion());
 }