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

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)

Committed: https://chromium.googlesource.com/chromium/src/+/07560fe8034f03b0b35771cfe9595762d3c0ad10

[trchen, 2016-05-20 23:33:49]

Description was changed from

==========
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)
==========

to

==========
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)

Committed:
https://chromium.googlesource.com/chromium/src/+/07560fe8034f03b0b35771cfe959...
==========

[trchen, 2016-05-20 23:33:50]

Committed patchset #1 (id:1) manually as
07560fe8034f03b0b35771cfe9595762d3c0ad10 (presubmit successful).