Only allocate a foreground layer for a CLM if there are composited negative-z-index-children.

Only allocate a foreground layer for a CLM if there are composited negative-z-index-children.

Otherwise, those children can be rendered as pat of the software rendering of the current
layer and its non-compositing descendants.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181424

[chrishtr, 2014-09-02 19:57:40]

chrishtr@chromium.org changed reviewers:
+ vollick@chromium.org

[chrishtr, 2014-09-02 19:57:40]

I *think* this handles all cases, but could be wrong.

The motivating example is from Baker's app, where there is a composited layer
with negative z-index children for drop shadows, but those shadows are not
individually composited. I don't think an extra layer is needed in that case?

[chrishtr, 2014-09-04 16:57:00]

Ping?

[Ian Vollick, 2014-09-04 17:00:33]

On 2014/09/04 16:57:00, chrishtr wrote:
> Ping?

I can't see a reason for the extra layer, either. This lgtm.

[chrishtr, 2014-09-04 17:01:31]

The CQ bit was checked by chrishtr@chromium.org

[commit-bot: I haz the power, 2014-09-04 17:02:47]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/chrishtr@chromium.org/535553002/1

[commit-bot: I haz the power, 2014-09-04 18:09:06]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-04 18:09:07]

Try jobs failed on following builders:
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/2...)

[chrishtr, 2014-09-04 20:32:16]

The CQ bit was checked by chrishtr@chromium.org

[commit-bot: I haz the power, 2014-09-04 20:33:38]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/chrishtr@chromium.org/535553002/20001

[commit-bot: I haz the power, 2014-09-05 00:26:59]

Committed patchset #2 (id:20001) as 181424