[New Multicolumn] Layout support for column-span:all.

Source/core/rendering/RenderBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 665 matching lines @@
     // invalidate our paint (and the child) anyway.
     if (!selfNeedsLayout() && (childOffset.width() || childOffset.height()))
         child.invalidatePaintForOverhangingFloats(true);
 
     if (paginated) {
         // Check for an after page/column break.
         LayoutUnit newHeight = applyAfterBreak(child, logicalHeight(), marginInfo);
         if (newHeight != height())
             setLogicalHeight(newHeight);
     }
+
+    if (child.isRenderMultiColumnSpannerPlaceholder()) {
+        // The actual column-span:all element is positioned by this placeholder child.
+        positionSpannerDescendant(toRenderMultiColumnSpannerPlaceholder(child));
+    }
 }
 
 LayoutUnit RenderBlockFlow::adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox& child, bool atBeforeSideOfBlock)
 {
     RenderBlockFlow* childBlockFlow = child.isRenderBlockFlow() ? toRenderBlockFlow(&child) : 0;
 
     if (estimateWithoutPagination != logicalTopAfterClear) {
         // Our guess prior to pagination movement was wrong. Before we attempt to paginate, let's try again at the new
         // position.
         setLogicalHeight(logicalTopAfterClear);
@@ skipping 357 matching lines @@
             adjustPositionedBlock(*child, marginInfo);
             continue;
         }
         if (child->isFloating()) {
             insertFloatingObject(*child);
             adjustFloatingBlock(marginInfo);
             continue;
         }
         if (child->isColumnSpanAll()) {
             // This is not the containing block of the spanner. The spanner's placeholder will lay
-            // it out in due course.
+            // it out in due course. For now we just need to consult our flow thread, so that the
+            // columns (if any) preceding and following the spanner are laid out correctly.
+            LayoutUnit adjustment = flowThreadContainingBlock()->skipColumnSpanner(child, offsetFromLogicalTopOfFirstPage() + logicalHeight());
+            setLogicalHeight(logicalHeight() + adjustment);
             continue;
         }
 
         // Lay out the child.
         layoutBlockChild(*child, marginInfo, previousFloatLogicalBottom);
         lastNormalFlowChild = child;
     }
 
     // Now do the handling of the bottom of the block, adding in our bottom border/padding and
     // determining the correct collapsed bottom margin information.
@@ skipping 1886 matching lines @@
 void RenderBlockFlow::setPaginationStrut(LayoutUnit strut)
 {
     if (!m_rareData) {
         if (!strut)
             return;
         m_rareData = adoptPtrWillBeNoop(new RenderBlockFlowRareData(this));
     }
     m_rareData->m_paginationStrut = strut;
 }
 
+void RenderBlockFlow::positionSpannerDescendant(RenderMultiColumnSpannerPlaceholder& child)
+{
+    RenderBox& spanner = *child.rendererInFlowThread();
+    // FIXME: |spanner| is a descendant, but never a direct child, so the names here are bad, if
+    // nothing else.
+    setLogicalTopForChild(spanner, child.logicalTop());
+    determineLogicalLeftPositionForChild(spanner);
+}
+
 bool RenderBlockFlow::avoidsFloats() const
 {
     // Floats can't intrude into our box if we have a non-auto column count or width.
     // Note: we need to use RenderBox::avoidsFloats here since RenderBlock::avoidsFloats is always true.
     return RenderBox::avoidsFloats() || !style()->hasAutoColumnCount() || !style()->hasAutoColumnWidth();
 }
 
 void RenderBlockFlow::moveChildrenTo(RenderBoxModelObject* toBoxModelObject, RenderObject* startChild, RenderObject* endChild, RenderObject* beforeChild, bool fullRemoveInsert)
 {
     if (childrenInline())
@@ skipping 128 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (height() < visibleHeight)
         top += (visibleHeight - height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink