Add out-of-flow descendants of spanners to their containing blocks in time.

Source/core/layout/LayoutBlock.cpp

Index: Source/core/layout/LayoutBlock.cpp
diff --git a/Source/core/layout/LayoutBlock.cpp b/Source/core/layout/LayoutBlock.cpp
index dd9facbf773689c89c04a2fa25bf0158e740a832..da8ce9cdd6dc3edb291c7b39fc23fb03abf9fcb6 100644
--- a/Source/core/layout/LayoutBlock.cpp
+++ b/Source/core/layout/LayoutBlock.cpp
@@ -1042,6 +1042,13 @@ bool LayoutBlock::createsNewFormattingContext() const
 
 void LayoutBlock::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, LayoutBox& child)
 {
+    if (child.isOutOfFlowPositioned()) {

[dsinclair, 2015/06/12 13:40:45]

Doesn't this mean that an out of flow child will never have the dirty bits
updated?

[mstensho (USE GERRIT), 2015/06/12 13:45:08]

The counterpart for out of flow objects seems to be in
LayoutBlock::layoutPositionedObjects(), wehre we do things like:

        if (relayoutChildren ||
needsLayoutDueToStaticPosition(positionedObject))
            layoutScope.setChildNeedsLayout(positionedObject);

and a bunch of other things.

+        // It's rather useless to mark out-of-flow children at this point. We may not be their
+        // containing block (and if we are, it's just pure luck), so this would be the wrong place
+        // for it. Furthermore, it would cause trouble for out-of-flow descendants of column
+        // spanners, if the containing block is outside the spanner but inside the multicol container.
+        return;
+    }
     // FIXME: Technically percentage height objects only need a relayout if their percentage isn't going to be turned into
     // an auto value. Add a method to determine this, so that we can avoid the relayout.
     bool hasRelativeLogicalHeight = child.hasRelativeLogicalHeight()