Surprisingly, the mentioned tests failed for the first time only in https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20Leak/builds/4931 and there were multiple failures before (starting from https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20Leak/builds/4925), but with different tests.

In the latest build only the 3 mentioned tests do fail (https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20Leak/builds/4936), so I will focus on them for now.

Relevant logs from the last failing build (https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20Leak/builds/4936):
=== LOG STARTS ===
1:49:54.071 6211 worker/3 fast/dom/inert/inert-inlines.html leaked
01:49:54.078 6044 [38120/55988] fast/dom/inert/inert-inlines.html failed unexpectedly (leak detected: ({"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,19],"numberOfLiveResources":[0,2],"numberOfLiveSuspendableObjects":[2,4]}))
01:49:54.071 6211 worker/3 fast/dom/inert/inert-inlines.html failed:
...
01:49:55.687 6211 worker/3 fast/dom/inert/inert-label-focus.html leaked
01:49:55.687 6211   Xlib:  extension "RANDR" missing on display ":99".
01:49:55.687 6211   #EOF
01:49:55.694 6044 [38175/55988] fast/dom/inert/inert-label-focus.html failed unexpectedly (leak detected: ({"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,17],"numberOfLiveResources":[0,2],"numberOfLiveSuspendableObjects":[2,3]}))
...
02:02:49.143 10205 worker/7 fast/dom/inert/inert-node-is-uneditable.html leaked
02:02:49.143 10205   Xlib:  extension "RANDR" missing on display ":99".
02:02:49.152 6044 [2/42] fast/dom/inert/inert-node-is-uneditable.html failed unexpectedly (leak detected: ({"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,21],"numberOfLiveResources":[0,2],"numberOfLiveSuspendableObjects":[2,3]}))
=== LOG ENDS ===

Further down the log is a bit different for inert-inlines (the last argument [2,3] instead of [2,4]):
=== LOG STARTS ===
02:02:52.836 10205 worker/7 fast/dom/inert/inert-inlines.html leaked
02:02:52.836 10205   Xlib:  extension "RANDR" missing on display ":99".
02:02:52.836 10205   #EOF
02:02:52.839 6044 [24/42] fast/dom/inert/inert-inlines.html failed unexpectedly (leak detected: ({"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,19],"numberOfLiveResources":[0,2],"numberOfLiveSuspendableObjects":[2,3]}))
=== LOG ENDS ===

I inspected Cls from the first build, where the 3 mentioned tests fail for the first time (https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20Leak/builds/4931). The most relevant one is https://codereview.chromium.org/2088453002, which actually adds these tests.

Reverting the CL.

The CL is too large to be reverted via codereview, reverting manually.

The CL cannot be reverted cleanly, conflicts:
third_party/WebKit/Source/core/frame/UseCounter.h
tools/metrics/histograms/enums.xml

due to https://chromium-review.googlesource.com/c/513902/

The revert is https://codereview.chromium.org/2902133002.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e353755ef5c7e109ddf2370ebacc39377924fc55

commit e353755ef5c7e109ddf2370ebacc39377924fc55
Author: vitaliii <vitaliii@chromium.org>
Date: Wed May 24 12:22:48 2017

Revert of "Implement the inert attribute"

The revert did not apply cleanly, there were conflicts in:
- third_party/WebKit/Source/core/frame/UseCounter.h
- tools/metrics/histograms/enums.xml

Reason for revert:
The new added tests leak. See  crbug.com/725815 .

Original issue's description:
> Implement the inert attribute: https://github.com/WICG/inert#tldr
>
> https://discourse.wicg.io/t/inert-attribute/1838/
>
> BUG=692360
> Review-Url: https://codereview.chromium.org/2088453002
> Cr-Commit-Position: refs/heads/master@{#474153}
> Committed: https://chromium.googlesource.com/chromium/src/+/cca67d31f4a0b4ec2c20090a8bfc38c464274ab2

TBR=aboxhall@chromium.org,hayato@chromium.org,dglazkov@chromium.org,esprehn@chromium.org,dmazzoni@chromium.org,kochi@chromium.org
BUG=692360, 725815 

Review-Url: https://codereview.chromium.org/2902133002
Cr-Commit-Position: refs/heads/master@{#474259}

[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/external/wpt/html/dom/elements/elements-in-the-dom/historical.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-does-not-match-disabled-selector.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-focus-in-frames.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-in-shadow-dom.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-inlines.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-label-focus.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-node-is-uneditable.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-node-is-unfocusable.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/inert-node-is-unselectable.html
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/resources/dialog-layout.css
[delete] https://crrev.com/a61ab21892d351e22b39b2a17c2b9948f6866525/third_party/WebKit/LayoutTests/fast/dom/inert/resources/inert-focus-in-frames-frame1.html
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/inspector-protocol/accessibility/accessibility-ignoredNodes-expected.txt
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/inspector-protocol/accessibility/accessibility-ignoredNodes.html
[add] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/platform/linux/inspector-protocol/accessibility/accessibility-ignoredNodes-expected.txt
[add] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/platform/win/inspector-protocol/accessibility/accessibility-ignoredNodes-expected.txt
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/virtual/service-worker-navigation-preload-disabled/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/webexposed/element-instance-property-listing-expected.txt
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/dom/Node.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/dom/Node.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/dom/Text.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/html/HTMLAttributeNames.json5
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/html/HTMLElement.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/core/html/HTMLElement.idl
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/devtools/front_end/accessibility/AccessibilityNodeView.js
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXMenuListOption.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXMenuListPopup.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXObjectCacheImpl.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXObjectCacheImpl.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXObjectImpl.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/AXObjectImpl.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/InspectorAccessibilityAgent.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/InspectorAccessibilityAgent.h
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/modules/accessibility/InspectorTypeBuilderHelper.cpp
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.json5
[modify] https://crrev.com/e353755ef5c7e109ddf2370ebacc39377924fc55/tools/metrics/histograms/enums.xml

The builder is green now.

https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20Leak/builds/4941