`branch-buttons` and `list-prs-for-file` break the layout #2624

<img width="999" alt="" src="https://user-images.githubusercontent.com/1402241/70723642-cf7b8780-1d2b-11ea-8b9c-331f332e0920.png">

branch-buttons can be fixed with a display: inline-flex or white-space: nowrap or something like that.

list-prs-for-file needs a better solution when there are more than 1-2 PRs open, maybe it could show a dropdown.

Test

https://github.com/microsoft/TypeScript/blob/07364595e4ca539578cf34eeb5a6efd452061d10/src/compiler/program.ts