Is it slow whenever you close the dialog or only when you try to link a bug? If the latter, the problem may be that the server sometimes takes a long time to respond to a new linked bug (it has to make a request to Monorail to get the bug title). 

The speed varies, but it's slow in both cases.

Aside: In general, I'm not a big fan of Material Design / Quantum Paper widgets for internal productivity tools. The tools are for expert users, so they don't need to look like consumer apps. Give me raw html <button> and high info density any day! :-)

That's useful to know. I'm not able to get it to take ~2 seconds without linking a bug but I'll keep watch. I don't think it's normal even with the flashy animation for it to take that long, so I think there might be some sort of performance bug in the UI here. 

Also, I agree with you on trying to make the design of the app a bit more lightweight/simple. This has been brought up by some users before, and I think you have a very good point, so I filed a bug for that too: https://bugs.chromium.org/p/chromium/issues/detail?id=720084

I am working on a few things which should hopefully improve the speed of the Sheriff-o-Matic frontend, including removing animations. 

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/f4ee02e1f8ab76903627003f0f92344c57ed479a

commit f4ee02e1f8ab76903627003f0f92344c57ed479a
Author: Tiff Zhang <zhangtiff@google.com>
Date: Wed May 17 19:11:18 2017

SoM: Start removing paper elements and adjust styling.

Bug:720084
Bug:720021

Change-Id: Idc821a25d27a9e1cf43b6ee78606c3c837733c32
Reviewed-on: https://chromium-review.googlesource.com/506615
Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Sean McCullough <seanmccullough@chromium.org>

[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-drawer/som-drawer.js
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-alert-item/som-alert-item.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-drawer/som-drawer.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-app/som-app.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-annotations/som-annotations.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-tree-status/som-tree-status.html
[add] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-input-styles.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-master-restarts/som-master-restarts.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/bower.json
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-header-styles.html

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/f4ee02e1f8ab76903627003f0f92344c57ed479a

commit f4ee02e1f8ab76903627003f0f92344c57ed479a
Author: Tiff Zhang <zhangtiff@google.com>
Date: Wed May 17 19:11:18 2017

SoM: Start removing paper elements and adjust styling.

Bug:720084
Bug:720021

Change-Id: Idc821a25d27a9e1cf43b6ee78606c3c837733c32
Reviewed-on: https://chromium-review.googlesource.com/506615
Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Sean McCullough <seanmccullough@chromium.org>

[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-drawer/som-drawer.js
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-alert-item/som-alert-item.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-drawer/som-drawer.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-app/som-app.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-annotations/som-annotations.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-tree-status/som-tree-status.html
[add] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-input-styles.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-master-restarts/som-master-restarts.html
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/bower.json
[modify] https://crrev.com/f4ee02e1f8ab76903627003f0f92344c57ed479a/go/src/infra/appengine/sheriff-o-matic/elements/som-header-styles.html

Several changes were made to try to speed up the frontend of Sheriff-o-Matic, but it is the sort of thing that can always be improved ever more. 

I'll go ahead and mark this as fixed since I think the link/file bug dialog is a lot snappier since when this was filed. But please feel free to comment here again or open a new issue if it's still slow. :)