Able to reproduce the issue on Windows 10, mac 10.12.3 and Ubuntu 14.04 using chrome reported version #56.0.2924.87 and latest canary #59.0.3043.0.

Bisect Information:
=====================
Good build: 55.0.2853.0      Revision(416812)

Bad Build : 55.0.2855.0      Revision(417475)

Change Log URL: 
https://chromium.googlesource.com/chromium/src/+log/30d9858f1399f7f7bba8260c80c4d032da35eba9..e15391d9a56a210cf5faee97c24bfad856225ea9

From the above change log suspecting below change

Review url: https://codereview.chromium.org/2306323002

tkent@ - Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Thanks...!!

It seems the change of childrenChange() in the CL caused this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e89e9ca08e4abca7bf13d7424434b301caf5b4a5

commit e89e9ca08e4abca7bf13d7424434b301caf5b4a5
Author: tkent <tkent@chromium.org>
Date: Thu Mar 23 08:08:16 2017

CSS Selector: Fix a regression of :first-child and :last-child invalidation

https://codereview.chromium.org/2306323002 caused a regression of :first-child and
:last-child invalidation because the timing of ContainerNode::childrenChanged was
slightly changed for multiple nodes insertion.
 Before: childrenChanged was called on every node insertion
 After: childrenChanged was called after inserting all nodes

This CL changes the definition of ChildrenChanged::siblingBeforeChange and
siblingAfterChange so that they always point existing nodes before insertion
operations. It fixes the behavior of ContainerNode::checkForSiblingStyleChanges,
which is called from Element::childrenChanged and ShadowRoot::childrenChanged.
siblingBeforeChange and siblingAfterChange are used only by
checkForSiblingStyleChanges.  So this definition change is safe.

BUG= 702104 

Review-Url: https://codereview.chromium.org/2772463004
Cr-Commit-Position: refs/heads/master@{#459023}

[add] https://crrev.com/e89e9ca08e4abca7bf13d7424434b301caf5b4a5/third_party/WebKit/LayoutTests/fast/css/invalidation/firstchild-lastchild-for-multiple-node-insertion.html
[modify] https://crrev.com/e89e9ca08e4abca7bf13d7424434b301caf5b4a5/third_party/WebKit/Source/core/dom/ContainerNode.cpp
[modify] https://crrev.com/e89e9ca08e4abca7bf13d7424434b301caf5b4a5/third_party/WebKit/Source/core/dom/ContainerNode.h

Your change meets the bar and is auto-approved for M58. Please go ahead and merge the CL to branch 3029 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), bhthompson@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/404689093a8d2aeb6345635948f614e35d0fdf3a

commit 404689093a8d2aeb6345635948f614e35d0fdf3a
Author: Kent Tamura <tkent@chromium.org>
Date: Fri Mar 24 08:20:24 2017

Merge "CSS Selector: Fix a regression of :first-child and :last-child invalidation" to M58.

https://codereview.chromium.org/2306323002 caused a regression of :first-child and
:last-child invalidation because the timing of ContainerNode::childrenChanged was
slightly changed for multiple nodes insertion.
 Before: childrenChanged was called on every node insertion
 After: childrenChanged was called after inserting all nodes

This CL changes the definition of ChildrenChanged::siblingBeforeChange and
siblingAfterChange so that they always point existing nodes before insertion
operations. It fixes the behavior of ContainerNode::checkForSiblingStyleChanges,
which is called from Element::childrenChanged and ShadowRoot::childrenChanged.
siblingBeforeChange and siblingAfterChange are used only by
checkForSiblingStyleChanges.  So this definition change is safe.

BUG= 702104 

Review-Url: https://codereview.chromium.org/2772463004
Cr-Commit-Position: refs/heads/master@{#459023}
(cherry picked from commit e89e9ca08e4abca7bf13d7424434b301caf5b4a5)

Review-Url: https://codereview.chromium.org/2774753003 .
Cr-Commit-Position: refs/branch-heads/3029@{#405}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}

[add] https://crrev.com/404689093a8d2aeb6345635948f614e35d0fdf3a/third_party/WebKit/LayoutTests/fast/css/invalidation/firstchild-lastchild-for-multiple-node-insertion.html
[modify] https://crrev.com/404689093a8d2aeb6345635948f614e35d0fdf3a/third_party/WebKit/Source/core/dom/ContainerNode.cpp
[modify] https://crrev.com/404689093a8d2aeb6345635948f614e35d0fdf3a/third_party/WebKit/Source/core/dom/ContainerNode.h

Verified this issue on Ubuntu 14.04, Mac OS 10.12 and Windows-10 using chrome latest Beta M58-58.0.3029.41. By opening the test case provided in the original comment observed the last child element get repainted as expected. Hence adding TE-Verified label.