Maybe related: https://bugs.chromium.org/p/chromium/issues/detail?id=702107#c4

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6

commit b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6
Author: skyostil <skyostil@chromium.org>
Date: Wed Apr 26 10:32:08 2017

headless: Add support for net logging

This patch adds support for the --log-net-log command line flag to
headless to help diagnosing issues with networking.

BUG= 706355 

Review-Url: https://codereview.chromium.org/2841953002
Cr-Commit-Position: refs/heads/master@{#467289}

[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/BUILD.gn
[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_browser_context_impl.cc
[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_browser_main_parts.cc
[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_browser_main_parts.h
[add] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_net_log.cc
[add] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_net_log.h
[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_url_request_context_getter.cc
[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/browser/headless_url_request_context_getter.h
[modify] https://crrev.com/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6/headless/lib/headless_browser_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7615988083fac48fe5410bb59a9e379853615aa8

commit 7615988083fac48fe5410bb59a9e379853615aa8
Author: findit-for-me <findit-for-me@appspot.gserviceaccount.com>
Date: Wed Apr 26 11:40:38 2017

Revert of headless: Add support for net logging (patchset #2 id:20001 of https://codereview.chromium.org/2841953002/ )

Reason for revert:

Findit(https://goo.gl/kROfz5) identified CL at revision 467289 as the
culprit for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2I5YTQyYWI2ZjA3M2IwNTdjOGMwNWQyYmZjNzk5ZGNjODA4MmUyYTYM

Sheriff's note:
See  crbug.com/715513  for details.

Original issue's description:
> headless: Add support for net logging
>
> This patch adds support for the --log-net-log command line flag to
> headless to help diagnosing issues with networking.
>
> BUG= 706355 
>
> Review-Url: https://codereview.chromium.org/2841953002
> Cr-Commit-Position: refs/heads/master@{#467289}
> Committed: https://chromium.googlesource.com/chromium/src/+/b9a42ab6f073b057c8c05d2bfc799dcc8082e2a6

TBR=eseckler@chromium.org,skyostil@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG= 706355 , 715513 

Review-Url: https://codereview.chromium.org/2839153002
Cr-Commit-Position: refs/heads/master@{#467297}

[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/BUILD.gn
[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/lib/browser/headless_browser_context_impl.cc
[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/lib/browser/headless_browser_main_parts.cc
[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/lib/browser/headless_browser_main_parts.h
[delete] https://crrev.com/7529b2aa9b7de2c64e424082b2ee09cad44e27c4/headless/lib/browser/headless_net_log.cc
[delete] https://crrev.com/7529b2aa9b7de2c64e424082b2ee09cad44e27c4/headless/lib/browser/headless_net_log.h
[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/lib/browser/headless_url_request_context_getter.cc
[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/lib/browser/headless_url_request_context_getter.h
[modify] https://crrev.com/7615988083fac48fe5410bb59a9e379853615aa8/headless/lib/headless_browser_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/86195291fae07e5bb665295e0cb598777100ff34

commit 86195291fae07e5bb665295e0cb598777100ff34
Author: skyostil <skyostil@chromium.org>
Date: Wed Apr 26 14:08:02 2017

headless: Add support for net logging

This patch adds support for the --log-net-log command line flag to
headless to help diagnosing issues with networking.

BUG= 706355 

Review-Url: https://codereview.chromium.org/2841953002
Review-Url: https://codereview.chromium.org/2841953002
Cr-Commit-Position: refs/heads/master@{#467315}

[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/BUILD.gn
[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_browser_context_impl.cc
[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_browser_main_parts.cc
[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_browser_main_parts.h
[add] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_net_log.cc
[add] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_net_log.h
[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_url_request_context_getter.cc
[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/browser/headless_url_request_context_getter.h
[modify] https://crrev.com/86195291fae07e5bb665295e0cb598777100ff34/headless/lib/headless_browser_browsertest.cc

https://www.bloomingdales.com seems to work now, also with older builds, so I'm guessing something changed at their end. I'll see if I can find other examples of failing sites.

Can't seem to reproduce this on anything anymore.

This may be an edge case but I can successfully reproduce with the following: 

--headless --disable-gpu --dump-dom https://www.bbcgoodfood.com/recipes/1869/chicken-noodle-soup
Network is my mobile hotspot, 4G but a bad connection. 

My working theory is that the request for the external script never completes and the DOM won't be dumped at all. I got the idea from here: https://developers.google.com/web/updates/2016/08/removing-document-write

I've tried the bloomingdales site. I get the same parser-blocking script message but the DOM is dumped successfully. 

This is just for info to try to track down the bug if it is ever reopened.