We have the same problem at our other Win10 Tester as well (build96-b1 at https://build.chromium.org/p/chromium.webrtc.fyi/builders/Win10%20Tester).

labs: Is this something that needs to be fixed in the Win10 image or has something happened with these particular machines? I remember we were pretty early with Win10, so maybe they have a non-standard image? We don't see this error on non-Win10 machines. 

Two things.  Yes, debugger is missing from Windows 10 image.  Will add it.

Also https://codereview.chromium.org/2365773002

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/547cdab7f263971624422ea5b8ac665981c26514

commit 547cdab7f263971624422ea5b8ac665981c26514
Author: pschmidt <pschmidt@google.com>
Date: Fri Sep 23 15:30:29 2016

Add Windows 10 location for debugger in process_dumps.py

BUG= 649291 

Review-Url: https://codereview.chromium.org/2365773002

[modify] https://crrev.com/547cdab7f263971624422ea5b8ac665981c26514/scripts/slave/process_dumps.py

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chrome/tools/build_limited/scripts/slave/+/0a41a122cf52c677aa027dd82df1524e3262731a

commit 0a41a122cf52c677aa027dd82df1524e3262731a
Author: recipe-roller <recipe-roller@chromium.org>
Date: Fri Sep 23 15:33:57 2016

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2c2a79b3c362d8c83e1b55b2b48fc76b0a800e45

commit 2c2a79b3c362d8c83e1b55b2b48fc76b0a800e45
Author: recipe-roller <recipe-roller@chromium.org>
Date: Fri Sep 23 16:27:13 2016

Roll recipe dependencies (trivial).

This is an automated CL created by the recipe roller. This CL rolls recipe
changes from upstream projects (e.g. depot_tools) into downstream projects
(e.g. tools/build).

More info is at https://goo.gl/zkKdpD. Use https://goo.gl/noib3a to file a bug
(or complain)

build:
  https://crrev.com/547cdab7f263971624422ea5b8ac665981c26514 Add Windows 10 location for debugger in process_dumps.py (pschmidt@google.com)

TBR=martiniss@chromium.org,phajdan.jr@chromium.org
BUG= 649291 

Recipe-Tryjob-Bypass-Reason: Autoroller
Bugdroid-Send-Email: False
Review-Url: https://codereview.chromium.org/2366883003
Cr-Commit-Position: refs/heads/master@{#420620}

[modify] https://crrev.com/2c2a79b3c362d8c83e1b55b2b48fc76b0a800e45/infra/config/recipes.cfg

This is working now.

Closing.