Consistently check if a block can handle pagination strut propagation.

https://codereview.chromium.org/1360753002 got it right for inline child
layout, but did nothing for block child layout.

BUG=329421
R=jchaffraix@chromium.org,leviw@chromium.org

Review URL: https://codereview.chromium.org/1387553002

Cr-Commit-Position: refs/heads/master@{#352429}
void LayoutBlockFlow::paintFloats(const PaintInfo& paintInfo, const LayoutPoint& paintOffset, bool preservePhase) const
{
    BlockFlowPainter(*this).paintFloats(paintInfo, paintOffset, preservePhase);
}

void LayoutBlockFlow::paintFloats(const PaintInfo& paintInfo, const LayoutPoint& paintOffset, bool preservePhase) const
{
    BlockFlowPainter(*this).paintFloats(paintInfo, paintOffset, preservePhase);
}
