*** DO NOT LAND *** Implement column-span:all without reparenting renderers. Work in progress.

Source/core/rendering/RenderBlockFlow.cpp

Index: Source/core/rendering/RenderBlockFlow.cpp
diff --git a/Source/core/rendering/RenderBlockFlow.cpp b/Source/core/rendering/RenderBlockFlow.cpp
index 61db8cc0f25e4d307e353709688fabd97d6d00e3..7dfe8dfd2287cd8a1630d12fa636e3851e376cb1 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -548,6 +548,15 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
 {
     LayoutUnit oldPosMarginBefore = maxPositiveMarginBefore();
     LayoutUnit oldNegMarginBefore = maxNegativeMarginBefore();
+    bool isColumnSpanner = child->isColumnSpanAll();
+
+    if (isColumnSpanner) {
+        // Margins of a column spanner cannot collapse with anything.
+        setLogicalHeight(logicalHeight() + marginInfo.margin());
+        marginInfo.clearMargin();
+        LayoutUnit adjustment = flowThreadContainingBlock()->enterColumnSpanner(child, logicalHeight());
+        setLogicalHeight(logicalHeight() + adjustment);
+    }
 
     // The child is a normal flow object. Compute the margins we will use for collapsing now.
     child->computeAndSetBlockDirectionMargins(this);
@@ -558,14 +567,6 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
     LayoutUnit estimateWithoutPagination;
     LayoutUnit logicalTopEstimate = estimateLogicalTopPosition(child, marginInfo, estimateWithoutPagination);
 
-    bool isColumnSpanner = child->isColumnSpanAll();
-    if (isColumnSpanner) {
-        LayoutUnit margin = child->marginBefore();
-        logicalTopEstimate -= margin;
-        flowThreadContainingBlock()->enterColumnSpanner(child, logicalTopEstimate);
-        logicalTopEstimate += margin;
-    }
-
     // Cache our old rect so that we can dirty the proper paint invalidation rects if the child moves.
     LayoutRect oldRect = child->frameRect();
     LayoutUnit oldLogicalTop = logicalTopForChild(child);
@@ -733,9 +734,6 @@ LayoutUnit RenderBlockFlow::adjustBlockChildForPagination(LayoutUnit logicalTopA
     // If the object has a page or column break value of "before", then we should shift to the top of the next page.
     LayoutUnit result = applyBeforeBreak(child, logicalTopAfterClear);
 
-    if (child->isColumnSpanAll())
-        result += flowThreadContainingBlock()->spannerLogicalTopAdjustment(child, result - child->marginBefore());
-
     // For replaced elements and scrolled elements, we want to shift them to the next page if they don't fit on the current one.
     LayoutUnit logicalTopBeforeUnsplittableAdjustment = result;
     LayoutUnit logicalTopAfterUnsplittableAdjustment = adjustForUnsplittableChild(child, result);
@@ -1183,7 +1181,7 @@ LayoutUnit RenderBlockFlow::collapseMargins(RenderBox* child, MarginInfo& margin
     // margins that will collapse with us.
     bool topQuirk = hasMarginBeforeQuirk(child);
 
-    if (marginInfo.canCollapseWithMarginBefore() && !mustSeparateMarginBeforeForChild(child)) {
+    if (marginInfo.canCollapseWithMarginBefore()) {
         if (!childDiscardMarginBefore && !marginInfo.discardMargin()) {
             // This child is collapsing with the top of the
             // block. If it has larger margin values, then we need to update
@@ -1468,9 +1466,6 @@ void RenderBlockFlow::marginBeforeEstimateForChild(RenderBox* child, LayoutUnit&
     if (!grandchildBox || grandchildBox->style()->clear() != CNONE)
         return;
 
-    if (childBlockFlow->mustSeparateMarginBeforeForChild(grandchildBox))
-        return;
-
     // Make sure to update the block margins now for the grandchild box so that we're looking at current values.
     if (grandchildBox->needsLayout()) {
         grandchildBox->computeAndSetBlockDirectionMargins(this);
@@ -1490,7 +1485,7 @@ LayoutUnit RenderBlockFlow::estimateLogicalTopPosition(RenderBox* child, const M
     // FIXME: We need to eliminate the estimation of vertical position, because when it's wrong we sometimes trigger a pathological
     // relayout if there are intruding floats.
     LayoutUnit logicalTopEstimate = logicalHeight();
-    if (!marginInfo.canCollapseWithMarginBefore() || mustSeparateMarginBeforeForChild(child)) {
+    if (!marginInfo.canCollapseWithMarginBefore()) {
         LayoutUnit positiveMarginBefore = 0;
         LayoutUnit negativeMarginBefore = 0;
         bool discardMarginBefore = false;
@@ -1685,8 +1680,7 @@ void RenderBlockFlow::setMaxMarginAfterValues(LayoutUnit pos, LayoutUnit neg)
 
 bool RenderBlockFlow::mustSeparateMarginBeforeForChild(const RenderBox* child) const
 {
-    if (child->isColumnSpanAll())
-        return true;
+    ASSERT(!child->selfNeedsLayout());
     const RenderStyle* childStyle = child->style();
     if (!child->isWritingModeRoot())
         return childStyle->marginBeforeCollapse() == MSEPARATE;
@@ -1699,8 +1693,7 @@ bool RenderBlockFlow::mustSeparateMarginBeforeForChild(const RenderBox* child) c
 
 bool RenderBlockFlow::mustSeparateMarginAfterForChild(const RenderBox* child) const
 {
-    if (child->isColumnSpanAll())
-        return true;
+    ASSERT(!child->selfNeedsLayout());
     const RenderStyle* childStyle = child->style();
     if (!child->isWritingModeRoot())
         return childStyle->marginAfterCollapse() == MSEPARATE;