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

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index 473f7f1a9bcdd39b4d9fc44d1191a959a9e5fc75..da4cbfa1391fbe76dab0e0900e7db94ef3ea754a 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -322,6 +322,13 @@ bool RenderObject::requiresAnonymousTableWrappers(const RenderObject* newChild)
     return false;
 }
 
+bool RenderObject::isValidColumnSpanAll() const
+{
+    ASSERT(style()->columnSpan() == ColumnSpanAll);
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    return flowThread && flowThread->isColumnSpanner(this);
+}
+
 void RenderObject::addChild(RenderObject* newChild, RenderObject* beforeChild)
 {
     ASSERT(isAllowedToModifyRenderTreeStructure(document()));
@@ -2369,6 +2376,9 @@ void RenderObject::insertedIntoTree()
 
     if (!isFloating() && parent()->childrenInline())
         parent()->dirtyLinesFromChangedChild(this);
+
+    if (RenderFlowThread* flowThread = parent()->flowThreadContainingBlock())
+        flowThread->flowThreadDescendantInserted(this);
 }
 
 void RenderObject::willBeRemovedFromTree()
@@ -2419,6 +2429,8 @@ void RenderObject::removeFromRenderFlowThreadRecursive(RenderFlowThread* renderF
             child->removeFromRenderFlowThreadRecursive(renderFlowThread);
     }
 
+    if (renderFlowThread && renderFlowThread != this)
+        renderFlowThread->flowThreadDescendantWillBeRemoved(this);
     setFlowThreadState(NotInsideFlowThread);
 }