Out of last 25 builds, it failed 11 times.

Let's look at the last 5 failures:

https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29/70794
* device_orientation/motion/detached-frame.html (asserts failed)

 
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29/70789

* external/wpt/html/browsers/history/the-history-interface/history_go_plus.html  (test timed out)

* external/wpt/html/infrastructure/urls/resolving-urls/query-encoding/utf-8.html (text diff)

* external/wpt/html/semantics/embedded-content/the-object-element/object-handler.html (asserts failed)
 
* fast/loader/stateobjects/state-url-sets-links-visited.html (text diff)
* http/tests/history/popstate-reload.html (test timed out, text diff)
* http/tests/history/replacestate-post-to-get.html (text diff)

* virtual/stable/http/tests/navigation/replacestate-updates-referrer.html (text diff)

https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29/70787

* device_orientation/motion/detached-frame.html (asserts failed)
* external/wpt/requestidlecallback/callback-iframe.html (test timed out)


https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29/70785
* device_orientation/motion/detached-frame.html (asserts failed)


https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29/70784

* editing/input/reveal-selection-having-stored-scroll-position.html (test timed out, text diff)

* external/wpt/html/browsers/browsing-the-web/history-traversal/persisted-user-state-restoration/scroll-restoration-navigation-samedoc.html (test timed out)

* external/wpt/html/browsers/history/the-history-interface/008.html (asserts failed)
* external/wpt/html/browsers/history/the-location-interface/location_hash.html (asserts failed)

* fast/history/scroll-restoration/scroll-restoration-push-replace.html (test timed out)
* fast/history/scroll-restoration/scroll-restoration-same-doc.html (test timed out)
* fast/loader/stateobjects/popstate-after-load-complete-body-inline-attribute.html (test timed out)

* fast/loader/stateobjects/pushstate-then-replacestate.html (test timed out)

* fast/loader/stateobjects/pushstate-with-fragment-urls-and-hashchange.html (test timed out)

* http/tests/event-timing/event-timing-bufferbeforeonload.html (asserts failed)

After counting:  

    3 * device_orientation/motion/detached-frame.html (asserts failed)
      1 * virtual/stable/http/tests/navigation/replacestate-updates-referrer.html (text diff)
      1 * http/tests/history/replacestate-post-to-get.html (text diff)
      1 * http/tests/history/popstate-reload.html (test timed out, text diff)
      1 * http/tests/event-timing/event-timing-bufferbeforeonload.html (asserts failed)
      1 * fast/loader/stateobjects/state-url-sets-links-visited.html (text diff)
      1 * fast/loader/stateobjects/pushstate-with-fragment-urls-and-hashchange.html (test timed out)
      1 * fast/loader/stateobjects/pushstate-then-replacestate.html (test timed out)
      1 * fast/loader/stateobjects/popstate-after-load-complete-body-inline-attribute.html (test timed out)
      1 * fast/history/scroll-restoration/scroll-restoration-same-doc.html (test timed out)
      1 * fast/history/scroll-restoration/scroll-restoration-push-replace.html (test timed out)
      1 * external/wpt/requestidlecallback/callback-iframe.html (test timed out)
      1 * external/wpt/html/semantics/embedded-content/the-object-element/object-handler.html (asserts failed)
      1 * external/wpt/html/infrastructure/urls/resolving-urls/query-encoding/utf-8.html (text diff)
      1 * external/wpt/html/browsers/history/the-location-interface/location_hash.html (asserts failed)
      1 * external/wpt/html/browsers/history/the-history-interface/history_go_plus.html  (test timed out)
      1 * external/wpt/html/browsers/history/the-history-interface/008.html (asserts failed)
      1 * external/wpt/html/browsers/browsing-the-web/history-traversal/persisted-user-state-restoration/scroll-restoration-navigation-samedoc.html (test timed out)
      1 * editing/input/reveal-selection-having-stored-scroll-position.html (test timed out, text diff)

I am disabling device_orientation/motion/detached-frame.html in https://chromium-review.googlesource.com/c/chromium/src/+/1170696.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4f48e20c2cd19e8358d2b1844f979933ed00a796

commit 4f48e20c2cd19e8358d2b1844f979933ed00a796
Author: vitaliii <vitaliii@chromium.org>
Date: Fri Aug 10 10:25:28 2018

Disable flaky d/motion/detached-frame.html (fails on Win7).

device_orientation/motion/detached-frame.html

TBR=rmcelrath@chromium.org
NOTRY=true


Bug:  873078 
Change-Id: I58d98a331c8d56937313d8f2db27652355c1a4f7
Reviewed-on: https://chromium-review.googlesource.com/1170696
Reviewed-by: vitaliii <vitaliii@chromium.org>
Commit-Queue: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582107}
[modify] https://crrev.com/4f48e20c2cd19e8358d2b1844f979933ed00a796/third_party/WebKit/LayoutTests/TestExpectations

Please have a look and reenable, thank you!

AFAICS the test's also flaky on other platforms: https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=device_orientation%2Fmotion%2Fdetached-frame.html

This test was deleted in https://crrev.com/c/1167994