The webkit_tests step is failing due to the  fast/forms/associatedFormControls-leak-nodes.html test on 3 different Linux builders (I haven't noticed it failing on other platforms - not sure if it runs everywhere or just on linux though). This has happened several times in a row now, and according to sheriff-o-mattic this seemed to start with revision range 437893 - 437901:

https://chromium.googlesource.com/chromium/src/+log/140c9756623a2e4357a1385726cb6d0e898addc3%5E..d8f3464da24b2cdc50ed3169e45d431299786edb?pretty=fuller

Nothing in that revision range jumps out to me as an obvious cause, but I'm relatively unfamiliar with this area of code. 


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Here's a snippet of the log output from a recent failure:


11:36:41.024 14902 "/usr/bin/wdiff --start-delete=##WDIFF_DEL## --end-delete=##WDIFF_END## --start-insert=##WDIFF_ADD## --end-insert=##WDIFF_END## /b/rr/tmpvn33Sx/w/layout-test-results/fast/forms/associatedFormControls-leak-nodes-expected.txt /b/rr/tmpvn33Sx/w/layout-test-results/fast/forms/associatedFormControls-leak-nodes-actual.txt" took 0.02s
11:36:41.115 14902 "ruby -I /b/c/b/linux_layout/src/third_party/WebKit/Tools/Scripts/webkitruby/PrettyPatch /b/c/b/linux_layout/src/third_party/WebKit/Tools/Scripts/webkitruby/PrettyPatch/prettify.rb /b/rr/tmpvn33Sx/w/layout-test-results/fast/forms/associatedFormControls-leak-nodes-diff.txt" took 0.09s
11:36:41.116 14814 [21922/47988] fast/forms/associatedFormControls-leak-nodes.html failed unexpectedly (text diff)
11:36:41.115 14902 worker/7 fast/forms/associatedFormControls-leak-nodes.html failed:
11:36:41.115 14902 worker/7  text diff

This was from https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty/builds/20940/steps/webkit_tests/logs/stdio

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