Delete UpdateLayerPositionsFlags

Delete UpdateLayerPositionsFlags

This CL removes the last "flag" from update layer positions. I've also factored
the pagination update out into a separate walk. We should actually defer this
walk until we actually want to paint because paint is the primary (only?)
consumer of this information. There doesn't appear to be a reason to update it
eagerly after every layout.

R=esprehn@chromium.org
BUG=382548
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179657

[esprehn, 2014-08-05 23:24:57]

https://codereview.chromium.org/443773002/diff/1/Source/core/rendering/Render...
File Source/core/rendering/RenderLayer.cpp (right):

https://codereview.chromium.org/443773002/diff/1/Source/core/rendering/Render...
Source/core/rendering/RenderLayer.cpp:284: updateDescendantDependentFlags();
Note that this (in the worst case) walks the children layers 3 times, and the
loop below a fourth.

[abarth-chromium, 2014-08-05 23:28:54]

https://codereview.chromium.org/443773002/diff/1/Source/core/rendering/Render...
File Source/core/rendering/RenderLayer.cpp (right):

https://codereview.chromium.org/443773002/diff/1/Source/core/rendering/Render...
Source/core/rendering/RenderLayer.cpp:284: updateDescendantDependentFlags();
By |this|, do you mean updateDescendantDependentFlags specifically or do you
mean updateLayerPositionsAfterLayout() more generally?

updateDescendantDependentFlags isn't new in this CL, despite it being on a green
line.  It used to be on line 273.  I can work on deleting it next if you like.

[esprehn, 2014-08-05 23:34:44]

Yeah I know none of it is new, I was just commenting that this thing is
walking the children of the tree potentially 3 times for every RenderLayer.
I don't know how often we come in here with dirty flags though, or how
often flags are dirty in general.

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[abarth-chromium, 2014-08-05 23:37:49]

On 2014/08/05 at 23:34:44, esprehn wrote:
> Yeah I know none of it is new, I was just commenting that this thing is
> walking the children of the tree potentially 3 times for every RenderLayer.
> I don't know how often we come in here with dirty flags though, or how
> often flags are dirty in general.

I should be able to remove updateDescendantDependentFlags.  There's no reason
for it to be here.

We should be able to defer the pagination stuff until the paint/hittesting phase
as well.

[esprehn, 2014-08-06 17:12:46]

lgtm

[abarth-chromium, 2014-08-06 20:00:34]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-08-06 20:02:26]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/abarth@chromium.org/443773002/1

[commit-bot: I haz the power, 2014-08-06 21:32:13]

Change committed as 179657