*** FOR PROTOTYPE PURPOSES ONLY! NOT INTENDED FOR COMMIT! ***

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 d67b5e39511905f6578f1a1c47e99d281444d520..e19de90fd0e4219a169366984ed35cd83458d6e8 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -282,40 +282,64 @@ void RenderBlockFlow::layoutBlock(bool relayoutChildren)
 
     SubtreeLayoutScope layoutScope(this);
 
+    m_layoutScope = &layoutScope;
+    m_pageLogicalHeight = 0;
+
+    preLayoutBlock(relayoutChildren, true);
+
     // Multiple passes might be required for column and pagination based layout
     // In the case of the old column code the number of passes will only be two
     // however, in the newer column code the number of passes could equal the
     // number of columns.
-    bool done = false;
-    LayoutUnit pageLogicalHeight = 0;
-    while (!done)
-        done = layoutBlockFlow(relayoutChildren, pageLogicalHeight, layoutScope);
+    bool done = postLayoutBlock();
+    while (!done) {
+        preLayoutBlock(relayoutChildren, true);
+        done = postLayoutBlock();
+    }
+    m_layoutScope = 0;
 }
 
-inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &pageLogicalHeight, SubtreeLayoutScope& layoutScope)
+void RenderBlockFlow::preLayoutBlock(bool relayoutChildren, bool traverseChildren)
 {
-    LayoutRepainter repainter(*this, checkForRepaintDuringLayout());
+    m_relayoutChildren = relayoutChildren;
+    preLayoutBlockFlow(traverseChildren);
+}
+
+bool RenderBlockFlow::postLayoutBlock()
+{
+    return postLayoutBlockFlow();
+}
+
+void RenderBlockFlow::preLayoutBlockFlow(bool traverseChildren)
+{
+    m_checkForRepaint = checkForRepaintDuringLayout();
+    m_oldBounds = LayoutRect();
+    m_oldOutlineBox = LayoutRect();
+    if (m_checkForRepaint) {
+        m_oldBounds = clippedOverflowRectForRepaint(containerForRepaint());
+        m_oldOutlineBox = outlineBoundsForRepaint(containerForRepaint(), 0);
+    }
 
     if (updateLogicalWidthAndColumnWidth())
-        relayoutChildren = true;
+        m_relayoutChildren = true;
 
     rebuildFloatsFromIntruding();
 
     bool pageLogicalHeightChanged = false;
-    bool hasSpecifiedPageLogicalHeight = false;
-    checkForPaginationLogicalHeightChange(pageLogicalHeight, pageLogicalHeightChanged, hasSpecifiedPageLogicalHeight);
+    m_hasSpecifiedPageLogicalHeight = false;
+    checkForPaginationLogicalHeightChange(m_pageLogicalHeight, pageLogicalHeightChanged, m_hasSpecifiedPageLogicalHeight);
 
     RenderView* renderView = view();
-    LayoutStateMaintainer statePusher(renderView, this, locationOffset(), hasColumns() || hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode(), pageLogicalHeight, pageLogicalHeightChanged, columnInfo());
+    m_statePusher = new LayoutStateMaintainer(renderView, this, locationOffset(), hasColumns() || hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode(), m_pageLogicalHeight, pageLogicalHeightChanged, columnInfo());
 
     // Regions changing widths can force us to relayout our children.
     RenderFlowThread* flowThread = flowThreadContainingBlock();
     if (logicalWidthChangedInRegions(flowThread))
-        relayoutChildren = true;
+        m_relayoutChildren = true;
     if (updateRegionsAndShapesLogicalSize(flowThread))
-        relayoutChildren = true;
-    if (!relayoutChildren && isRenderNamedFlowFragmentContainer())
-        relayoutChildren = true;
+        m_relayoutChildren = true;
+    if (!m_relayoutChildren && isRenderNamedFlowFragmentContainer())
+        m_relayoutChildren = true;
 
     // We use four values, maxTopPos, maxTopNeg, maxBottomPos, and maxBottomNeg, to track
     // our current maximal positive and negative margins. These values are used when we
@@ -336,12 +360,12 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
 
     LayoutUnit beforeEdge = borderBefore() + paddingBefore();
     LayoutUnit afterEdge = borderAfter() + paddingAfter() + scrollbarLogicalHeight();
-    LayoutUnit previousHeight = logicalHeight();
+    m_heightBeforeLayout = logicalHeight();
     setLogicalHeight(beforeEdge);
 
     m_repaintLogicalTop = 0;
     m_repaintLogicalBottom = 0;
-    LayoutUnit maxFloatLogicalBottom = 0;
+    m_maxFloatLogicalBottom = 0;
     if (!firstChild() && !isAnonymousBlock())
         setChildrenInline(true);
 
@@ -350,15 +374,42 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
         textAutosizer->beginLayout(this);
 
     if (childrenInline())
-        layoutInlineChildren(relayoutChildren, m_repaintLogicalTop, m_repaintLogicalBottom, afterEdge);
-    else
-        layoutBlockChildren(relayoutChildren, maxFloatLogicalBottom, layoutScope, beforeEdge, afterEdge);
+        layoutInlineChildren(m_relayoutChildren, m_repaintLogicalTop, m_repaintLogicalBottom, afterEdge);
+    else {
+        dirtyForLayoutFromPercentageHeightDescendants(*m_layoutScope);
+
+        // Lay out our hypothetical grid line as though it occurs at the top of the block.
+        if (view()->layoutState()->lineGrid() == this)
+            layoutLineGridBox();
+
+        layoutBlockChildren(beforeEdge, afterEdge, traverseChildren);
+    }
+}
+
+bool RenderBlockFlow::postLayoutBlockFlow()
+{
+    if (!m_statePusher) // simple layout
+        return true;
 
     if (frameView()->partialLayout().isStopping()) {
-        statePusher.pop();
+        m_statePusher->pop();
+        delete m_statePusher;
+        m_statePusher = 0;
         return true;
     }
 
+    LayoutRepainter repainter(*this, m_checkForRepaint, m_oldBounds, m_oldOutlineBox);
+    LayoutUnit beforeEdge = borderBefore() + paddingBefore();
+    LayoutUnit afterEdge = borderAfter() + paddingAfter() + scrollbarLogicalHeight();
+
+    if (!childrenInline()) {
+        // Now do the handling of the bottom of the block, adding in our bottom border/padding and
+        // determining the correct collapsed bottom margin information.
+        handleAfterSideOfBlock(m_lastNormalFlowChild, beforeEdge, afterEdge, *m_marginInfo);
+        delete m_marginInfo;
+        m_marginInfo = 0;
+    }
+
     // Expand our intrinsic height to encompass floats.
     if (lowestFloatLogicalBottom() > (logicalHeight() - afterEdge) && createsBlockFormattingContext())
         setLogicalHeight(lowestFloatLogicalBottom() + afterEdge);
@@ -366,7 +417,9 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
     if (isRenderMultiColumnBlock()) {
         if (toRenderMultiColumnBlock(this)->shouldRelayoutMultiColumnBlock()) {
             setChildNeedsLayout(MarkOnlyThis);
-            statePusher.pop();
+            m_statePusher->pop();
+            delete m_statePusher;
+            m_statePusher = 0;
             return false;
         }
     } else if (hasColumns()) {
@@ -378,17 +431,21 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
         LayoutUnit layoutOverflowLogicalBottom = (isHorizontalWritingMode() ? layoutOverflowRect().maxY() : layoutOverflowRect().maxX()) - borderBefore() - paddingBefore();
         m_overflow = savedOverflow.release();
 
-        if (!hasSpecifiedPageLogicalHeight && shouldRelayoutForPagination(pageLogicalHeight, layoutOverflowLogicalBottom)) {
-            statePusher.pop();
+        if (!m_hasSpecifiedPageLogicalHeight && shouldRelayoutForPagination(m_pageLogicalHeight, layoutOverflowLogicalBottom)) {
+            m_statePusher->pop();
+            delete m_statePusher;
+            m_statePusher = 0;
             setEverHadLayout(true);
             return false;
         }
 
-        setColumnCountAndHeight(ceilf((float)layoutOverflowLogicalBottom / pageLogicalHeight), pageLogicalHeight);
+        setColumnCountAndHeight(ceilf((float)layoutOverflowLogicalBottom / m_pageLogicalHeight), m_pageLogicalHeight);
     }
 
     if (shouldBreakAtLineToAvoidWidow()) {
-        statePusher.pop();
+        m_statePusher->pop();
+        delete m_statePusher;
+        m_statePusher = 0;
         setEverHadLayout(true);
         return false;
     }
@@ -405,7 +462,7 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
     updateLogicalHeight();
     LayoutUnit newHeight = logicalHeight();
     if (oldHeight != newHeight) {
-        if (oldHeight > newHeight && maxFloatLogicalBottom > newHeight && !childrenInline()) {
+        if (oldHeight > newHeight && m_maxFloatLogicalBottom > newHeight && !childrenInline()) {
             // One of our children's floats may have become an overhanging float for us. We need to look for it.
             for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
                 if (child->isRenderBlockFlow() && !child->isFloatingOrOutOfFlowPositioned()) {
@@ -417,26 +474,29 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
         }
     }
 
-    bool heightChanged = (previousHeight != newHeight);
+    bool heightChanged = (m_heightBeforeLayout != newHeight);
     if (heightChanged)
-        relayoutChildren = true;
+        m_relayoutChildren = true;
 
-    layoutPositionedObjects(relayoutChildren || isRoot());
+    layoutPositionedObjects(m_relayoutChildren || isRoot());
 
-    updateRegionsAndShapesAfterChildLayout(flowThread, heightChanged);
+    updateRegionsAndShapesAfterChildLayout(flowThreadContainingBlock(), heightChanged);
 
     // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
     computeOverflow(oldClientAfterEdge);
 
-    statePusher.pop();
+    m_statePusher->pop();
 
     fitBorderToLinesIfNeeded();
 
-    if (frameView()->partialLayout().isStopping())
+    if (frameView()->partialLayout().isStopping()) {
+        delete m_statePusher;
+        m_statePusher = 0;
         return true;
+    }
 
-    if (renderView->layoutState()->m_pageLogicalHeight)
-        setPageLogicalOffset(renderView->layoutState()->pageLogicalOffset(this, logicalTop()));
+    if (view()->layoutState()->m_pageLogicalHeight)
+        setPageLogicalOffset(view()->layoutState()->pageLogicalOffset(this, logicalTop()));
 
     updateLayerTransform();
 
@@ -453,17 +513,36 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
             repaintOverflow();
     }
 
+    FastTextAutosizer* textAutosizer = document().fastTextAutosizer();
     if (textAutosizer)
         textAutosizer->endLayout(this);
 
     clearNeedsLayout();
+    delete m_statePusher;
+    m_statePusher = 0;

[esprehn, 2014/02/15 00:35:43]

This should be an OwnPtr you just clear.

     return true;
 }
 
-void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, LayoutUnit& previousFloatLogicalBottom, LayoutUnit& maxFloatLogicalBottom)
+bool RenderBlockFlow::preLayoutBlockChild(RenderBox* child, bool& skipChildren)
 {
-    LayoutUnit oldPosMarginBefore = maxPositiveMarginBefore();
-    LayoutUnit oldNegMarginBefore = maxNegativeMarginBefore();
+    updateBlockChildDirtyBitsBeforeLayout(m_relayoutChildren, child);
+
+    if (child->isOutOfFlowPositioned()) {
+        child->containingBlock()->insertPositionedObject(child);
+        adjustPositionedBlock(child, *m_marginInfo);
+        skipChildren = true;
+        return false;
+    }
+
+    if (child->isFloating()) {
+        insertFloatingObject(child);
+        adjustFloatingBlock(*m_marginInfo);
+        skipChildren = true;
+        return false;
+    }
+
+    m_oldPosMarginBefore = maxPositiveMarginBefore();
+    m_oldNegMarginBefore = maxNegativeMarginBefore();
 
     // The child is a normal flow object. Compute the margins we will use for collapsing now.
     child->computeAndSetBlockDirectionMargins(this);
@@ -471,25 +550,25 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
     // Try to guess our correct logical top position. In most cases this guess will
     // be correct. Only if we're wrong (when we compute the real logical top position)
     // will we have to potentially relayout.
-    LayoutUnit estimateWithoutPagination;
-    LayoutUnit logicalTopEstimate = estimateLogicalTopPosition(child, marginInfo, estimateWithoutPagination);
+    m_estimateWithoutPagination = 0;
+    m_logicalTopEstimate = estimateLogicalTopPosition(child, *m_marginInfo, m_estimateWithoutPagination);
 
     // Cache our old rect so that we can dirty the proper repaint rects if the child moves.
-    LayoutRect oldRect = child->frameRect();
+    m_oldRect = child->frameRect();
     LayoutUnit oldLogicalTop = logicalTopForChild(child);
 
 #if !ASSERT_DISABLED
-    LayoutSize oldLayoutDelta = RuntimeEnabledFeatures::repaintAfterLayoutEnabled() ? LayoutSize() : view()->layoutDelta();
+    m_oldLayoutDelta = RuntimeEnabledFeatures::repaintAfterLayoutEnabled() ? LayoutSize() : view()->layoutDelta();
 #endif
     // Go ahead and position the child as though it didn't collapse with the top.
-    setLogicalTopForChild(child, logicalTopEstimate, ApplyLayoutDelta);
+    setLogicalTopForChild(child, m_logicalTopEstimate, ApplyLayoutDelta);
 
     RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
     RenderBlockFlow* childRenderBlockFlow = (childRenderBlock && child->isRenderBlockFlow()) ? toRenderBlockFlow(child) : 0;
     bool markDescendantsWithFloats = false;
-    if (logicalTopEstimate != oldLogicalTop && !child->avoidsFloats() && childRenderBlock && childRenderBlock->containsFloats()) {
+    if (m_logicalTopEstimate != oldLogicalTop && !child->avoidsFloats() && childRenderBlock && childRenderBlock->containsFloats()) {
         markDescendantsWithFloats = true;
-    } else if (UNLIKELY(logicalTopEstimate.mightBeSaturated())) {
+    } else if (UNLIKELY(m_logicalTopEstimate.mightBeSaturated())) {
         // logicalTopEstimate, returned by estimateLogicalTopPosition, might be saturated for
         // very large elements. If it does the comparison with oldLogicalTop might yield a
         // false negative as adding and removing margins, borders etc from a saturated number
@@ -498,8 +577,8 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
     } else if (!child->avoidsFloats() || child->shrinkToAvoidFloats()) {
         // If an element might be affected by the presence of floats, then always mark it for
         // layout.
-        LayoutUnit fb = max(previousFloatLogicalBottom, lowestFloatLogicalBottom());
-        if (fb > logicalTopEstimate)
+        LayoutUnit fb = max(m_previousFloatLogicalBottom, lowestFloatLogicalBottom());
+        if (fb > m_logicalTopEstimate)
             markDescendantsWithFloats = true;
     }
 
@@ -507,43 +586,58 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
         if (markDescendantsWithFloats)
             childRenderBlockFlow->markAllDescendantsWithFloatsForLayout();
         if (!child->isWritingModeRoot())
-            previousFloatLogicalBottom = max(previousFloatLogicalBottom, oldLogicalTop + childRenderBlockFlow->lowestFloatLogicalBottom());
+            m_previousFloatLogicalBottom = max(m_previousFloatLogicalBottom, oldLogicalTop + childRenderBlockFlow->lowestFloatLogicalBottom());
     }
 
-    SubtreeLayoutScope layoutScope(child);
+    m_childLayoutScope = new SubtreeLayoutScope(child);
     if (!child->needsLayout())
-        child->markForPaginationRelayoutIfNeeded(layoutScope);
-
-    bool childHadLayout = child->everHadLayout();
-    bool childNeededLayout = child->needsLayout();
-    if (childNeededLayout)
-        child->layout();
+        child->markForPaginationRelayoutIfNeeded(*m_childLayoutScope);
+
+    m_childHadLayout = child->everHadLayout();
+    m_childNeededLayout = child->needsLayout();

[esprehn, 2014/02/15 00:35:43]

This doesn't feel right. Storing so much state in the render object is not good.

[atreat, 2014/02/18 16:03:57]

Right, see the comment in the header file.  We'll need to figure out where/how
to store this state.

+    skipChildren |= !m_childNeededLayout;
+    if (m_childNeededLayout) {
+        if (child->isNonRecursiveLayout())
+            child->preLayout();
+        else
+            child->layout();
+    }
+    return true;
+}
 
-    if (frameView()->partialLayout().isStopping())
+void RenderBlockFlow::postLayoutBlockChild(RenderBox* child)
+{
+    if (child->isOutOfFlowPositioned() || child->isFloating())
         return;
 
+    if (m_childNeededLayout && child->isNonRecursiveLayout())
+        child->postLayout();
+
     // Cache if we are at the top of the block right now.
-    bool atBeforeSideOfBlock = marginInfo.atBeforeSideOfBlock();
+    bool atBeforeSideOfBlock = m_marginInfo->atBeforeSideOfBlock();
 
     // Now determine the correct ypos based off examination of collapsing margin
     // values.
-    LayoutUnit logicalTopBeforeClear = collapseMargins(child, marginInfo);
+    LayoutUnit logicalTopBeforeClear = collapseMargins(child, *m_marginInfo);
 
     // Now check for clear.
-    LayoutUnit logicalTopAfterClear = clearFloatsIfNeeded(child, marginInfo, oldPosMarginBefore, oldNegMarginBefore, logicalTopBeforeClear);
+    LayoutUnit logicalTopAfterClear = clearFloatsIfNeeded(child, *m_marginInfo, m_oldPosMarginBefore, m_oldNegMarginBefore, logicalTopBeforeClear);
 
     bool paginated = view()->layoutState()->isPaginated();
     if (paginated) {
-        logicalTopAfterClear = adjustBlockChildForPagination(logicalTopAfterClear, estimateWithoutPagination, child,
+        logicalTopAfterClear = adjustBlockChildForPagination(logicalTopAfterClear, m_estimateWithoutPagination, child,
             atBeforeSideOfBlock && logicalTopBeforeClear == logicalTopAfterClear);
     }
 
     setLogicalTopForChild(child, logicalTopAfterClear, ApplyLayoutDelta);
 
+    RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
+    RenderBlockFlow* childRenderBlockFlow = (childRenderBlock && child->isRenderBlockFlow()) ? toRenderBlockFlow(child) : 0;
+
     // Now we have a final top position. See if it really does end up being different from our estimate.
     // clearFloatsIfNeeded can also mark the child as needing a layout even though we didn't move. This happens
     // when collapseMargins dynamically adds overhanging floats because of a child with negative margins.
-    if (logicalTopAfterClear != logicalTopEstimate || child->needsLayout() || (paginated && childRenderBlock && childRenderBlock->shouldBreakAtLineToAvoidWidow())) {
+    if (logicalTopAfterClear != m_logicalTopEstimate || child->needsLayout() || (paginated && childRenderBlock && childRenderBlock->shouldBreakAtLineToAvoidWidow())) {
         SubtreeLayoutScope layoutScope(child);
         if (child->shrinkToAvoidFloats()) {
             // The child's width depends on the line width.
@@ -568,30 +662,30 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
     // we set this bit to ensure we would not collapse the child's margins, and those of any subsequent
     // self-collapsing siblings, with our parent. If this child is not self-collapsing then it can
     // collapse its margins with the parent so reset the bit.
-    if (!marginInfo.canCollapseMarginAfterWithLastChild() && !child->isSelfCollapsingBlock())
-        marginInfo.setCanCollapseMarginAfterWithLastChild(true);
+    if (!m_marginInfo->canCollapseMarginAfterWithLastChild() && !child->isSelfCollapsingBlock())
+        m_marginInfo->setCanCollapseMarginAfterWithLastChild(true);
 
     // We are no longer at the top of the block if we encounter a non-empty child.
     // This has to be done after checking for clear, so that margins can be reset if a clear occurred.
-    if (marginInfo.atBeforeSideOfBlock() && !child->isSelfCollapsingBlock())
-        marginInfo.setAtBeforeSideOfBlock(false);
+    if (m_marginInfo->atBeforeSideOfBlock() && !child->isSelfCollapsingBlock())
+        m_marginInfo->setAtBeforeSideOfBlock(false);
 
     // Now place the child in the correct left position
     determineLogicalLeftPositionForChild(child, ApplyLayoutDelta);
 
-    LayoutSize childOffset = child->location() - oldRect.location();
+    LayoutSize childOffset = child->location() - m_oldRect.location();
     relayoutShapeDescendantIfMoved(childRenderBlock, childOffset);
 
     // Update our height now that the child has been placed in the correct position.
     setLogicalHeight(logicalHeight() + logicalHeightForChild(child));
     if (mustSeparateMarginAfterForChild(child)) {
         setLogicalHeight(logicalHeight() + marginAfterForChild(child));
-        marginInfo.clearMargin();
+        m_marginInfo->clearMargin();
     }
     // If the child has overhanging floats that intrude into following siblings (or possibly out
     // of this block), then the parent gets notified of the floats now.
     if (childRenderBlockFlow && childRenderBlockFlow->containsFloats())
-        maxFloatLogicalBottom = max(maxFloatLogicalBottom, addOverhangingFloats(childRenderBlockFlow, !childNeededLayout));
+        m_maxFloatLogicalBottom = max(m_maxFloatLogicalBottom, addOverhangingFloats(childRenderBlockFlow, !m_childNeededLayout));
 
     if (childOffset.width() || childOffset.height()) {
         if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
@@ -600,13 +694,13 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
         // If the child moved, we have to repaint it as well as any floating/positioned
         // descendants. An exception is if we need a layout. In this case, we know we're going to
         // repaint ourselves (and the child) anyway.
-        if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled() && childHadLayout && !selfNeedsLayout())
+        if (RuntimeEnabledFeatures::repaintAfterLayoutEnabled() && m_childHadLayout && !selfNeedsLayout())
             child->repaintOverhangingFloats(true);
-        else if (childHadLayout && !selfNeedsLayout() && child->checkForRepaintDuringLayout())
-            child->repaintDuringLayoutIfMoved(oldRect);
+        else if (m_childHadLayout && !selfNeedsLayout() && child->checkForRepaintDuringLayout())
+            child->repaintDuringLayoutIfMoved(m_oldRect);
     }
 
-    if (!childHadLayout && child->checkForRepaint()) {
+    if (!m_childHadLayout && child->checkForRepaint()) {
         if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
             child->repaint();
         child->repaintOverhangingFloats(true);
@@ -614,14 +708,18 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
 
     if (paginated) {
         // Check for an after page/column break.
-        LayoutUnit newHeight = applyAfterBreak(child, logicalHeight(), marginInfo);
+        LayoutUnit newHeight = applyAfterBreak(child, logicalHeight(), *m_marginInfo);
         if (newHeight != height())
             setLogicalHeight(newHeight);
     }
 
     if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled()) {
-        ASSERT(view()->layoutDeltaMatches(oldLayoutDelta));
+        ASSERT(view()->layoutDeltaMatches(m_oldLayoutDelta));
     }
+
+    m_lastNormalFlowChild = child;
+    delete m_childLayoutScope;
+    m_childLayoutScope = 0;
 }
 
 LayoutUnit RenderBlockFlow::adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox* child, bool atBeforeSideOfBlock)
@@ -848,63 +946,67 @@ void RenderBlockFlow::rebuildFloatsFromIntruding()
     }
 }
 
-void RenderBlockFlow::layoutBlockChildren(bool relayoutChildren, LayoutUnit& maxFloatLogicalBottom, SubtreeLayoutScope& layoutScope, LayoutUnit beforeEdge, LayoutUnit afterEdge)
+void RenderBlockFlow::layoutBlockChildren(LayoutUnit beforeEdge, LayoutUnit afterEdge, bool traverseChildren)
 {
-    dirtyForLayoutFromPercentageHeightDescendants(layoutScope);
-
-    // Lay out our hypothetical grid line as though it occurs at the top of the block.
-    if (view()->layoutState()->lineGrid() == this)
-        layoutLineGridBox();
-
     // The margin struct caches all our current margin collapsing state. The compact struct caches state when we encounter compacts,
-    MarginInfo marginInfo(this, beforeEdge, afterEdge);
+    m_marginInfo = new MarginInfo(this, beforeEdge, afterEdge);

[esprehn, 2014/02/15 00:35:43]

Adding more mallocs doesn't seem like the right way to go. Now you cause a
malloc per block as we walk down the tree.

 
     // Fieldsets need to find their legend and position it inside the border of the object.
     // The legend then gets skipped during normal layout. The same is true for ruby text.
     // It doesn't get included in the normal layout process but is instead skipped.
-    RenderObject* childToExclude = layoutSpecialExcludedChild(relayoutChildren, layoutScope);
+    m_childToExclude = layoutSpecialExcludedChild(m_relayoutChildren, *m_layoutScope);
+    m_previousFloatLogicalBottom = 0;
+    m_maxFloatLogicalBottom = 0;
+    m_lastNormalFlowChild = 0;
 
-    LayoutUnit previousFloatLogicalBottom = 0;
-    maxFloatLogicalBottom = 0;
+    if (!traverseChildren)
+        return;
 
-    RenderBox* next = firstChildBox();
-    RenderBox* lastNormalFlowChild = 0;
+    bool skippingChildren = false;
+#if NON_RECURSIVE
+    Order order = Pre;
+    RenderObject* childObject = nextForLayout(order, this, skippingChildren);
+    for (; childObject && childObject != this; childObject = childObject->nextForLayout(order, this, skippingChildren)) {
+        if (!childObject->isBox())
+            continue;
+        RenderBox *child = toRenderBox(childObject);
+        skippingChildren = child->childrenInline();
+#else
+    (void)skippingChildren;
+    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
+#endif
 
-    while (next) {
-        RenderBox* child = next;
-        next = child->nextSiblingBox();
+        ASSERT(child->parent()->isRenderBlockFlow());
+        RenderBlockFlow* directParent = toRenderBlockFlow(child->parent());
 
         LayoutRectRecorder recorder(*child);
-
-        if (childToExclude == child)
+        if (directParent->m_childToExclude == child) {
+            skippingChildren = true;
             continue; // Skip this child, since it will be positioned by the specialized subclass (fieldsets and ruby runs).
+        }
 
-        updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, child);
+#if NON_RECURSIVE
+        if (order == Pre) {
+#endif
 
-        if (child->isOutOfFlowPositioned()) {
-            child->containingBlock()->insertPositionedObject(child);
-            adjustPositionedBlock(child, marginInfo);
-            continue;
-        }
-        if (child->isFloating()) {
-            insertFloatingObject(child);
-            adjustFloatingBlock(marginInfo);
+        // Lay out the child.
+        if (!directParent->preLayoutBlockChild(child, skippingChildren))
             continue;
-        }
 
-        // Lay out the child.
-        layoutBlockChild(child, marginInfo, previousFloatLogicalBottom, maxFloatLogicalBottom);
-        lastNormalFlowChild = child;
+#if NON_RECURSIVE
+        } else {
+#endif
+
+        directParent->postLayoutBlockChild(child);
+
+#if NON_RECURSIVE
+        }
+#endif
 
         // If doing a partial layout and the child was the target renderer, early exit here.
         if (frameView()->partialLayout().checkPartialLayoutComplete(child))
             return;
-
     }
-
-    // Now do the handling of the bottom of the block, adding in our bottom border/padding and
-    // determining the correct collapsed bottom margin information.
-    handleAfterSideOfBlock(lastNormalFlowChild, beforeEdge, afterEdge, marginInfo);
 }
 
 // Our MarginInfo state used when laying out block children.