`Mac_ios stable flutter_gallery_ios__start_up` repeatedly timing out

https://ci.chromium.org/p/flutter/builders/prod/Mac_ios%20stable%20flutter_gallery_ios__start_up/4

```
[flutter_gallery_ios__start_up] [STDOUT] stdout: [   +7 ms] Connected to iPhone
[flutter_gallery_ios__start_up] [STDOUT] stdout: [        ] Tracing startup on iPhone.
[flutter_gallery_ios__start_up] [STDOUT] stdout: [   +4 ms] Waiting for application to render first frame...
```