I'll take this. Want to use the new Swarming mixins martiniss@ added to define the GPU bots and unify them across the GPU / V8 waterfalls.

On the other hand I think that likely the configs are the same, though there are some weird infra failures like:
https://ci.chromium.org/p/v8/builders/luci.v8.ci/Mac%20V8%20FYI%20Release%20%28Intel%29/2851

which don't show up on the GPU waterfall. Could those be network connectivity problems?

https://chromium-review.googlesource.com/1287431 up for review, refactoring the GPU bots' configurations to use Swarming mixins.

mb_config.pyl is already correctly factored to reuse the configuration parameters from the chromium.gpu(.fyi) bots for the GPU bots on the client.v8.fyi waterfall.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/73c3bd8bd89cda7ae0d8692baef93cb98792bace

commit 73c3bd8bd89cda7ae0d8692baef93cb98792bace
Author: Kenneth Russell <kbr@chromium.org>
Date: Fri Oct 19 22:30:19 2018

Use mixins for GPU bot configurations.

Define and use mixins for the most common GPU bot configurations. To
avoid errors and differences between machines, in most of these mixins,
parameters like the OS have been flattened in.

Use these mixins on the chromium.gpu, chromium.gpu.fyi, and
client.v8.fyi waterfalls.

This CL is essentially a no-op; it only modifies a few timeouts due to
unification under the mixin "limited_capacity_bot".

Bug:  895815 
Change-Id: Ia9da945d73720ea70ebb4983808eb23463ee1108
Reviewed-on: https://chromium-review.googlesource.com/c/1287431
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601324}
[modify] https://crrev.com/73c3bd8bd89cda7ae0d8692baef93cb98792bace/testing/buildbot/chromium.gpu.fyi.json
[modify] https://crrev.com/73c3bd8bd89cda7ae0d8692baef93cb98792bace/testing/buildbot/generate_buildbot_json.py
[modify] https://crrev.com/73c3bd8bd89cda7ae0d8692baef93cb98792bace/testing/buildbot/generate_buildbot_json_unittest.py
[modify] https://crrev.com/73c3bd8bd89cda7ae0d8692baef93cb98792bace/testing/buildbot/mixins.pyl
[modify] https://crrev.com/73c3bd8bd89cda7ae0d8692baef93cb98792bace/testing/buildbot/waterfalls.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/576d15f6389dc77ff1fcd8c42dd754b34cf28ced

commit 576d15f6389dc77ff1fcd8c42dd754b34cf28ced
Author: Kenneth Russell <kbr@chromium.org>
Date: Thu Oct 25 00:54:18 2018

Switch client.v8.fyi 'Win V8 FYI Release (NVIDIA)' to Win10.

This is a difference in configuration between the chromium.gpu and
client.v8.fyi waterfalls.

Tbr: machenbach@chromium.org
Bug:  895815 
Change-Id: I758b9acf46ce49b192d7f8d811c73a05b572d7c2
Reviewed-on: https://chromium-review.googlesource.com/c/1298497
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602544}
[modify] https://crrev.com/576d15f6389dc77ff1fcd8c42dd754b34cf28ced/testing/buildbot/client.v8.fyi.json
[modify] https://crrev.com/576d15f6389dc77ff1fcd8c42dd754b34cf28ced/testing/buildbot/waterfalls.pyl

Optimistically closing this as Fixed. The configurations should be well aligned now. Please reopen or file a new bug if there are any issues with the GPU bots on V8's waterfall.