Switch DPLStackingNode to use LayoutBoxModelObject

Switch DPLStackingNode to use LayoutBoxModelObject

DeprecatedPaintLayerStackingNode was using DeprecatedPaintLayer
internally. DeprecatedPaintLayer is the wrong abstraction to
build our concept of stacking context on top of so this change
switches DPLStackingNode to use LayoutBoxModelObject instead.
This means that we will potentially walk the tree more (as we
don't use the sparse-ish DeprecatedPaintLayer tree) but it
brings DPLStackingNode closer to the concept of a "stacking
context".

BUG=504125
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197785

[Julien - ping for review, 2015-06-24 16:56:54]

jchaffraix@chromium.org changed reviewers:
+ dsinclair@chromium.org, pdr@chromium.org

[Julien - ping for review, 2015-06-24 16:56:55]

Moar DeprecatedPaintLayerStackingNode simplification

[dsinclair, 2015-06-24 19:40:50]

lgtm w/ nits

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
File Source/core/paint/DeprecatedPaintLayerStackingNode.cpp (right):

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
Source/core/paint/DeprecatedPaintLayerStackingNode.cpp:158: // stacking context.
However we can't make store them in the lists unless they have a
DeprecatedPaintLayer.
I think you have an extra make in that sentence.

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
File Source/core/paint/DeprecatedPaintLayerStackingNode.h (right):

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
Source/core/paint/DeprecatedPaintLayerStackingNode.h:96: DeprecatedPaintLayer*
layer() const;
Should we consider adding an ASSERT in here and a disabler so we don't add more
callers or are there just too many to do that at the moment?

crbug to fix?

[Julien - ping for review, 2015-06-24 21:40:00]

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

[Julien - ping for review, 2015-06-24 21:40:00]

+Chris as an FYI

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
File Source/core/paint/DeprecatedPaintLayerStackingNode.cpp (right):

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
Source/core/paint/DeprecatedPaintLayerStackingNode.cpp:158: // stacking context.
However we can't make store them in the lists unless they have a
DeprecatedPaintLayer.
On 2015/06/24 at 19:40:50, dsinclair wrote:
> I think you have an extra make in that sentence.

Removed.

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
File Source/core/paint/DeprecatedPaintLayerStackingNode.h (right):

https://codereview.chromium.org/1199413006/diff/1/Source/core/paint/Deprecate...
Source/core/paint/DeprecatedPaintLayerStackingNode.h:96: DeprecatedPaintLayer*
layer() const;
On 2015/06/24 at 19:40:50, dsinclair wrote:
> Should we consider adding an ASSERT in here and a disabler so we don't add
more callers or are there just too many to do that at the moment?

We could make it private and whitelist the classes / functions using it (seems
cleaner than an ASSERT triggering IMHO).

> crbug to fix?

I am not sure about where the whole effort would go, right now I am just
exploring the dependencies. I filed a bug (crbug.com/504125) as it's a good
direction.

[Julien - ping for review, 2015-06-24 23:28:47]

The CQ bit was checked by jchaffraix@chromium.org

[Julien - ping for review, 2015-06-24 23:28:48]

The patchset sent to the CQ was uploaded after l-g-t-m from
dsinclair@chromium.org
Link to the patchset: https://codereview.chromium.org/1199413006/#ps20001
(title: "Removed extra 'make'")

[commit-bot: I haz the power, 2015-06-24 23:29:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1199413006/20001

[commit-bot: I haz the power, 2015-06-24 23:32:19]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197785