[New Multicolumn] Create RenderMultiColumnSet during renderer creation, not during layout.

Source/core/rendering/RenderMultiColumnSet.cpp

Index: Source/core/rendering/RenderMultiColumnSet.cpp
diff --git a/Source/core/rendering/RenderMultiColumnSet.cpp b/Source/core/rendering/RenderMultiColumnSet.cpp
index 718b852090815b5231389ad9c9ea04590fb45077..e54c7a0fb38a6a2638aec6ef87eec4361eef7283 100644
--- a/Source/core/rendering/RenderMultiColumnSet.cpp
+++ b/Source/core/rendering/RenderMultiColumnSet.cpp
@@ -45,14 +45,24 @@ RenderMultiColumnSet::RenderMultiColumnSet(RenderFlowThread* flowThread)
 {
 }
 
-RenderMultiColumnSet* RenderMultiColumnSet::createAnonymous(RenderFlowThread* flowThread)
+RenderMultiColumnSet* RenderMultiColumnSet::createAnonymous(RenderFlowThread* flowThread, RenderStyle* parentStyle)
 {
     Document& document = flowThread->document();
     RenderMultiColumnSet* renderer = new RenderMultiColumnSet(flowThread);
     renderer->setDocumentForAnonymous(&document);
+    renderer->setStyle(RenderStyle::createAnonymousStyleWithDisplay(parentStyle, BLOCK));
     return renderer;
 }
 
+RenderMultiColumnSet* RenderMultiColumnSet::nextSiblingMultiColumnSet() const
+{
+    for (RenderObject* sibling = nextSibling(); sibling; sibling = sibling->nextSibling()) {
+        if (sibling->isRenderMultiColumnSet())
+            return toRenderMultiColumnSet(sibling);
+    }
+    return 0;
+}
+
 LayoutUnit RenderMultiColumnSet::heightAdjustedForSetOffset(LayoutUnit height) const
 {
     RenderBlockFlow* multicolBlock = multiColumnBlockFlow();