Since @page border box layout objects aren't in the the layout tree, any
code that wants to walk up the tree to find the containing block will be
in for a surprise.

This would happen if percentage-based @page padding was used [1].
Recomputing padding during painting when we have already done it during
layout is rather pointless anyway. Read it out directly from the
fragment.

[1] #1 blink::LayoutBox::ContainingBlockLogicalWidthForContent()
    #2 blink::LayoutBoxModelObject::ComputedCSSPadding()
    #3 blink::LayoutBoxModelObject::PaddingTop()
    #4 blink::LayoutBoxModelObject::PaddingOutsets()
    #5 blink::BoxPainterBase::PaintFillLayer()
    #6 blink::BoxPainterBase::PaintFillLayers()
    #7 blink::BoxFragmentPainter::PaintBackground()

Bug: 40286153
Change-Id: I1e6e92c2ce1d81aab2673ec9a877eac455534102
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5526469
Commit-Queue: Morten Stenshorne <[email protected]>
Reviewed-by: Xianzhu Wang <[email protected]>
Reviewed-by: Ian Kilpatrick <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1300711}