This needs to be committed for M52, and merged into M51. Blocking stable as a result.

Is this bug applicable to all or any specific Os?

Also M51 Stable is launching very soon! Your bug is labelled as Stable ReleaseBlock, pls make sure to land the fix and get it merged ASAP. All changes MUST be merged into the release branch by 5pm on May 20 to make into the desktop Stable final build cut. Thank you!

Ok, thank you. Please note that we're VERY close to M51 stable launch. Please try to resolve this ASAP (see comment #3 for more details).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9d8ea9509008c684392a42d688dfd3ababdf9f66

commit 9d8ea9509008c684392a42d688dfd3ababdf9f66
Author: trchen <trchen@chromium.org>
Date: Fri May 20 00:15:49 2016

Use counters for opacity with transform-style:preserve-3d

This CL add a use counter for elements that have opacity, preserve-3d,
and 3D-transformed descendants at the same time.

This is done as a part of CSS transform spec research to collect statistics
about compatibility quirks. Currently all vendors implement this corner case
as applying opacity to each descendant planes separately, but latest W3C
editor's draft recommends forcing transform-style to flat.

BUG= 612913 ,598917

Review-Url: https://codereview.chromium.org/1987283003
Cr-Commit-Position: refs/heads/master@{#394920}

[modify] https://crrev.com/9d8ea9509008c684392a42d688dfd3ababdf9f66/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/9d8ea9509008c684392a42d688dfd3ababdf9f66/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
[modify] https://crrev.com/9d8ea9509008c684392a42d688dfd3ababdf9f66/third_party/WebKit/Source/core/paint/PaintLayer.h
[modify] https://crrev.com/9d8ea9509008c684392a42d688dfd3ababdf9f66/tools/metrics/histograms/histograms.xml

Manually rebased for M51: https://codereview.chromium.org/2001803002/

Ping for merge approval. Thanks!

Before we approve merge to M51, Could you please confirm whether this change is baked/verified in Canary and safe to merge?

Yes, it was landed yesterday afternoon and so far I don't see fires.

Your change meets the bar and is auto-approved for M51 (branch: 2704)

We're very close to M51 Stable launch. Please merge your change to M51 branch 2704 ASAP or latest by 5pm on May 23, Monday. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/07560fe8034f03b0b35771cfe9595762d3c0ad10

commit 07560fe8034f03b0b35771cfe9595762d3c0ad10
Author: Tien-Ren Chen <trchen@chromium.org>
Date: Fri May 20 23:31:18 2016

Use counters for opacity with transform-style:preserve-3d

This CL add a use counter for elements that have opacity, preserve-3d,
and 3D-transformed descendants at the same time.

This is done as a part of CSS transform spec research to collect statistics
about compatibility quirks. Currently all vendors implement this corner case
as applying opacity to each descendant planes separately, but latest W3C
editor's draft recommends forcing transform-style to flat.

BUG= 612913 ,598917

Review-Url: https://codereview.chromium.org/1987283003
Cr-Commit-Position: refs/heads/master@{#394920}
(cherry picked from commit 9d8ea9509008c684392a42d688dfd3ababdf9f66)

Review URL: https://codereview.chromium.org/2001803002 .

Cr-Commit-Position: refs/branch-heads/2704@{#628}
Cr-Branched-From: 6e53600def8f60d8c632fadc70d7c1939ccea347-refs/heads/master@{#386251}

[modify] https://crrev.com/07560fe8034f03b0b35771cfe9595762d3c0ad10/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/07560fe8034f03b0b35771cfe9595762d3c0ad10/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
[modify] https://crrev.com/07560fe8034f03b0b35771cfe9595762d3c0ad10/third_party/WebKit/Source/core/paint/PaintLayer.h
[modify] https://crrev.com/07560fe8034f03b0b35771cfe9595762d3c0ad10/tools/metrics/histograms/histograms.xml