Able to reproduce this issue on Mac OS 10.12.6 using chrome latest dev #62.0.3198.0.

Bisect Information:
-------------------
You are probably looking for a change made after 483682 (known good), but no later than 483683 (first known bad).

CHANGELOG URL:
--------------
https://chromium.googlesource.com/chromium/src/+log/203a2bad8062d170441af80f574e897bc586f180..7c44da721a59e6aa0b9fdcddb314175cb1e0123f

@rune: 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!!

Minimized demo attached.

Deleted: ib.html 142 bytes

ib.html 142 bytes View Download

https://chromium-review.googlesource.com/c/chromium/src/+/643269

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3e112a3211482b35130baf32cf28e7d4a7705a95

commit 3e112a3211482b35130baf32cf28e7d4a7705a95
Author: Rune Lillesveen <rune@opera.com>
Date: Thu Aug 31 05:56:09 2017

Setup AttachContext correctly when attaching pseudo elements.

AttachContext.previous_in_flow was not set up correctly when attaching
pseudo elements. That caused incorrect whitespace attachment in some
cases. In order to do this, the AttachContext for children is set up in
Element instead of ContainerNode as ::before and ::after are attached
in Element before/after ContainerNode::AttachLayoutTree.

I have separated the creation and attachment of pseudo elements.
CreatePseudoElementIfNeeded now only creates the pseudo element.
Previously pseudo elements were sometimes attached as part of style
recalc, at which point we don't have a previous_in_flow to pass in.
This is also good for our goal of separating style recalc and layout
tree construction completely.

We still create pseudo elements when attaching a layout tree if these
pseudo elements are inside a subtree being (re-)attached. When we start
constructing ComputedStyle for elements in sub-trees being re-attached
in RecalcStyle instead of LayoutTreeBuilder, we can fully rely on
pseudo elements being generated for RecalcStyle.

The modified test expectations are actually a revert of what was
changed when landing the WhitespaceAttacher.

Bug:  759532 
Change-Id: Ic9f0f61d8c78bc8df7c5e589444a54583c78d763
Reviewed-on: https://chromium-review.googlesource.com/643269
Reviewed-by: nainar <nainar@chromium.org>
Commit-Queue: Rune Lillesveen <rune@opera.com>
Cr-Commit-Position: refs/heads/master@{#498767}
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/LayoutTests/fast/block/float/float-not-removed-from-pre-block-expected.txt
[add] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/LayoutTests/fast/text/whitespace/attach-whitespace-after-before-pseudo-expected.html
[add] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/LayoutTests/fast/text/whitespace/attach-whitespace-after-before-pseudo.html
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/LayoutTests/platform/linux/css2.1/t1204-root-e-expected.txt
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/LayoutTests/platform/mac/css2.1/t1204-root-e-expected.txt
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/LayoutTests/platform/win/css2.1/t1204-root-e-expected.txt
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/ContainerNode.cpp
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/Element.cpp
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/Element.h
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/Node.cpp
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/Node.h
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/PseudoElement.cpp
[modify] https://crrev.com/3e112a3211482b35130baf32cf28e7d4a7705a95/third_party/WebKit/Source/core/dom/Text.cpp

 Issue 771437  has been merged into this issue.