[New Multicolumn] Add support for column-span:all

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index 711b4af53f44cbb468e3d0391f5c0177cf72cf2d..9127e420432a82fbfe7738d705f12786530809f3 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -1073,9 +1073,6 @@ void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
     child->children()->setFirstChild(0);
     child->m_next = nullptr;
 
-    // Remove all the information in the flow thread associated with the leftover anonymous block.
-    child->removeFromRenderFlowThread();
-
     // RenderGrid keeps track of its children, we must notify it about changes in the tree.
     if (child->parent()->isRenderGrid())
         toRenderGrid(child->parent())->dirtyGrid();
@@ -1519,7 +1516,7 @@ void RenderBlock::addVisualOverflowFromTheme()
 bool RenderBlock::createsBlockFormattingContext() const
 {
     return isInlineBlockOrInlineTable() || isFloatingOrOutOfFlowPositioned() || hasOverflowClip() || isFlexItemIncludingDeprecated()
-        || style()->specifiesColumns() || isRenderFlowThread() || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot() || isDocumentElement() || style()->columnSpan();
+        || style()->specifiesColumns() || isRenderFlowThread() || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot() || isDocumentElement() || (document().regionBasedColumnsEnabled() ? isColumnSpanAll() : style()->columnSpan());
 }
 
 void RenderBlock::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, RenderBox* child)