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

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 d65f741ff88c6f6488d9b67be75c46320848aff7..20164e019d3a005ea6590ececd5523e0fc62f8fb 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -648,6 +648,8 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
         LayoutUnit newHeight = applyAfterBreak(child, logicalHeight(), marginInfo);
         if (newHeight != height())
             setLogicalHeight(newHeight);
+        if (RenderFlowThread* flowThread = flowThreadContainingBlock())
+            flowThread->flowThreadDescendantBoxLaidOut(child, offsetFromLogicalTopOfFirstPage() + newHeight);

[Julien - ping for review, 2014/06/18 00:51:59]

I don't like this pattern because it makes little sense to notify your container
that you were laid out as it is the one calling layout on you.

[mstensho (USE GERRIT), 2014/08/26 09:43:57]

Done.

[mstensho (USE GERRIT), 2014/08/26 09:43:57]

Got rid of this by setting 'always' on column-break-before, rather than on
column-break-after on the spanner placeholder. This way, things (positions and
sizes) are in a good shape right after layout, so we can tell the flow thread to
advance to the next column set as part of regular layout, rather than having a
hook in RenderBlockFlow.

I wasn't too proud of this hook in RenderBlockFlow myself, but last time I tried
to use column-break-before:always on the spanner (this was before the summer),
it didn't work. But someone must have fixed something during the summer. :)

     }
 
     if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled()) {
@@ -1884,9 +1886,23 @@ void RenderBlockFlow::addChild(RenderObject* newChild, RenderObject* beforeChild
         flowThread->addChild(newChild, beforeChild);
         return;
     }
+    if (beforeChild) {
+        if (RenderFlowThread* containingFlowThread = flowThreadContainingBlock())
+            beforeChild = containingFlowThread->resolveMovedChild(beforeChild);
+    }
     RenderBlock::addChild(newChild, beforeChild);
 }
 
+void RenderBlockFlow::removeChild(RenderObject* oldChild)
+{
+    if (!documentBeingDestroyed()) {
+        RenderFlowThread* flowThread = multiColumnFlowThread();
+        if (flowThread && flowThread != oldChild)
+            flowThread->flowThreadRelativeWillBeRemoved(oldChild);
+    }
+    RenderBlock::removeChild(oldChild);
+}
+
 void RenderBlockFlow::moveAllChildrenIncludingFloatsTo(RenderBlock* toBlock, bool fullRemoveInsert)
 {
     RenderBlockFlow* toBlockFlow = toRenderBlockFlow(toBlock);