In this attempted rebaseline tryjob:
https://ci.chromium.org/buildbot/tryserver.blink/win10-blink-rel/1078

from this CL:
https://chromium-review.googlesource.com/1264542

this shard failed a significant number (>100) of layout tests, unrelated to my patch:
https://chromium-swarm.appspot.com/task?id=405ebe1669bf0e10&refresh=10&show_raw=1

It's unclear to me whether this is a misconfiguration of the VM or something similar. It's since successfully run at least one shard of another webkit_layout_test run:
https://chromium-swarm.appspot.com/bot?id=win10-727f49a0-us-west1-b-55zz&sort_stats=total%3Adesc

Other webkit_layout_test tryjobs on win10-blink-rel didn't seem to be affected by this issue.
https://ci.chromium.org/buildbot/tryserver.blink/win10-blink-rel/?limit=200

The job did ultimately succeed due to erikchen's new "retry with patch" step. It was just very slow - just over 3 hours.

Marking P3 in case this can be investigated and some root cause found which could make layout tests more reliable.

     external/wpt/css/css-text/text-align/text-align-justify-004.html
     external/wpt/css/css-text/white-space/pre-wrap-006.html
     external/wpt/xhr/send-content-type-string.htm
     fast/events/drop-generate-user-gesture.html
     fast/multicol/vertical-rl/float-content-break.html
     fast/peerconnection/RTCPeerConnection-garbagecollected.html
     http/tests/cache/loaded-from-cache-after-reload-within-iframe.html
     http/tests/devtools/resource-har-conversion.js
     http/tests/fetch/window/stream-reader-base-https-other-https.html
     http/tests/fetch/window/stream-reader.html
     http/tests/history/redirect-307.html
     http/tests/htmlimports/import-custom-element-order.html
     http/tests/htmlimports/import-dynamic-block-async.html
     http/tests/htmlimports/import-dynamic-descendant-block.html
     http/tests/htmlimports/import-normalize-321.html
     http/tests/incremental/doc-write-before-end.pl
     http/tests/inspector-protocol/network/interception-auth-provide-credentials.js
     http/tests/inspector-protocol/network/redirect-interception-blocked.js
     http/tests/inspector-protocol/network/redirect-interception-modified.js
     http/tests/local/fileapi/send-sliced-dragged-file.html
     http/tests/misc/svg-image-in-content.html
     http/tests/security/contentSecurityPolicy/1.1/form-action-leak-path-on-redirect.html
     http/tests/security/contentSecurityPolicy/1.1/form-action-src-get-allowed.html
     http/tests/security/contentSecurityPolicy/1.1/plugintypes-affects-cross-site-child-disallowed.html
     http/tests/security/contentSecurityPolicy/script-src-self-blocked-03.html
     http/tests/security/contentSecurityPolicy/source-list-parsing-02.html
     http/tests/security/originHeader/origin-header-for-data.html
     http/tests/security/xssAuditor/embed-tag-javascript-url.html
     http/tests/security/xssAuditor/embed-tag-null-char.html
     http/tests/security/xssAuditor/full-block-get-from-iframe.html
     http/tests/security/xssAuditor/full-block-javascript-link.html
     http/tests/security/xssAuditor/iframe-injection.html
     http/tests/security/xssAuditor/iframe-javascript-url-twice-url-encode.html
     http/tests/security/xssAuditor/iframe-onload-in-svg-tag.html
     http/tests/security/xssAuditor/iframe-srcdoc.html
     http/tests/security/xssAuditor/inline-event-HTML-entities.html
     http/tests/security/xssAuditor/javascript-link-url-encoded.html
     http/tests/security/xssAuditor/open-iframe-src-03.html
     http/tests/security/xssAuditor/property-escape-noquotes.html
     http/tests/security/xssAuditor/property-escape-quote-03.html
     http/tests/security/xssAuditor/report-script-tag.html
     http/tests/security/xssAuditor/script-tag-Big5-char-twice-url-encode.html
     http/tests/security/xssAuditor/script-tag-Big5-char2.html
     http/tests/security/xssAuditor/script-tag-with-fancy-unicode.html
     http/tests/security/xssAuditor/script-tag-with-trailing-comment5.html
     http/tests/security/xssAuditor/xss-protection-parsing-03.html
     http/tests/sendbeacon/beacon-cookie.html
     http/tests/webfont/fontface-style-change.html
     http/tests/webfont/fontfaceset-status-attribute.html
     http/tests/webfont/slow-loading.html
     http/tests/xmlhttprequest/origin-header-same-origin-post-async.html
     http/tests/xmlhttprequest/post-content-type.html
     http/tests/xmlhttprequest/serialize-document.html
     http/tests/xmlhttprequest/web-apps/004.html
     printing/webgl-repeated-printing.html
     sensor/magnetometer.html
     virtual/layout_ng/fast/block/float/nopaint-after-layer-destruction.html
     virtual/mouseevent_fractional/fast/events/keydown-numpad-keys.html
     virtual/outofblink-cors-ns/external/wpt/fetch/api/redirect/redirect-count.any.html
     virtual/outofblink-cors-ns/http/tests/navigation/form-targets-cross-site-frame-post.html
     virtual/outofblink-cors-ns/http/tests/navigation/post-basic.html
     virtual/outofblink-cors-ns/http/tests/navigation/redirect302-metaredirect.html
     virtual/outofblink-cors-ns/http/tests/navigation/success200-frames-loadsame.html
     virtual/outofblink-cors-ns/http/tests/security/XFrameOptions/x-frame-options-deny-delete-frame-in-load-event.html
     virtual/outofblink-cors-ns/http/tests/security/contentSecurityPolicy/1.1/plugintypes-url-01.html
     virtual/outofblink-cors-ns/http/tests/security/contentSecurityPolicy/source-list-parsing-05.html
     virtual/outofblink-cors-ns/http/tests/security/contentSecurityPolicy/source-list-parsing-09.html
     virtual/outofblink-cors-ns/http/tests/security/contentSecurityPolicy/source-list-parsing-paths-02.html
     virtual/outofblink-cors-ns/http/tests/security/contentTypeOptions/nosniff-script-blocked.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/base-href-null-char.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/embed-tag-code-attribute.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/embed-tag-in-path-unterminated.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/javascript-link-one-plus-one.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/link-onclick-entities.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/link-opens-new-window.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/object-tag-javascript-url.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/open-attribute-body.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/report-script-tag-cross-origin-https.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/report-script-tag-full-block.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/script-tag-Big5-char.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/script-tag-addslashes-null-char.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/script-tag-post-null-char.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/script-tag-replaced-with-questionmark.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/script-tag-with-source-control-char.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/script-tag-with-source.html
     virtual/outofblink-cors-ns/http/tests/security/xssAuditor/svg-animate.html
     virtual/outofblink-cors-ns/http/tests/xmlhttprequest/methods-lower-case.html
     virtual/outofblink-cors-ns/http/tests/xmlhttprequest/origin-header-same-origin-get-sync.html
     virtual/outofblink-cors-ns/http/tests/xmlhttprequest/web-apps/003.html
     virtual/outofblink-cors-ns/http/tests/xmlhttprequest/web-apps/010.html
     virtual/outofblink-cors-ns/http/tests/xmlhttprequest/workers/shared-worker-referer.html
     virtual/outofblink-cors/external/wpt/fetch/api/redirect/redirect-count.any.worker.html
     virtual/outofblink-cors/external/wpt/fetch/api/request/request-keepalive-quota.html?include=slow-2
     virtual/outofblink-cors/http/tests/navigation/success200-subframeload.html
     virtual/outofblink-cors/http/tests/security/contentSecurityPolicy/1.1/plugintypes-affects-child.html
     virtual/outofblink-cors/http/tests/security/contentSecurityPolicy/directive-parsing-multiple-headers.html
     virtual/outofblink-cors/http/tests/security/contentSecurityPolicy/nonces/scriptnonce-blocked.html
     virtual/outofblink-cors/http/tests/security/contentSecurityPolicy/script-src-redirect.html
     virtual/outofblink-cors/http/tests/security/contentSecurityPolicy/script-src-self-blocked-01.html
     virtual/outofblink-cors/http/tests/security/contentSecurityPolicy/source-list-parsing-nonascii.html
     virtual/outofblink-cors/http/tests/security/link-crossorigin-preload-use-credentials.html
     virtual/outofblink-cors/http/tests/security/originHeader/origin-header-for-empty.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/link-onclick-ampersand.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/open-iframe-src-01.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/property-escape-noquotes-tab-slash-chars.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/script-tag-inside-svg-tag3.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/script-tag-with-16bit-unicode-surrogate-pair.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/script-tag-with-16bit-unicode4.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/script-tag-with-source-entities.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/script-tag-with-source-same-host-with-query.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/script-tag-with-three-times-url-encoded-16bit-unicode.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/svg-script-tag-href.html
     virtual/outofblink-cors/http/tests/security/xssAuditor/xss-filter-bypass-big5.html
     virtual/outofblink-cors/http/tests/xmlhttprequest/encode-request-url.html
     virtual/outofblink-cors/http/tests/xmlhttprequest/origin-header-same-origin-post-sync.html
     virtual/outofblink-cors/http/tests/xmlhttprequest/post-with-boundary.html
     virtual/outofblink-cors/http/tests/xmlhttprequest/reopen-encoding.html
     virtual/outofblink-cors/http/tests/xmlhttprequest/send-document-content-type-charset.html
     virtual/outofblink-cors/http/tests/xmlhttprequest/workers/referer.html
     virtual/stable/http/tests/navigation/error404-basic.html
     virtual/stable/http/tests/navigation/form-targets-cross-site-frame-post.html
     virtual/stable/http/tests/navigation/post-goback1.html
     virtual/threaded/printing/standards-percentage-heights.html
     virtual/user-activation-v2/fast/events/popup-blocked-from-fake-button-click.html
     virtual/user-activation-v2/fast/events/popup-blocked-from-fake-focus.html