Replace RenderArena with PartitionAlloc

Source/core/rendering/RenderNamedFlowThread.cpp

Index: Source/core/rendering/RenderNamedFlowThread.cpp
diff --git a/Source/core/rendering/RenderNamedFlowThread.cpp b/Source/core/rendering/RenderNamedFlowThread.cpp
index 5537e81f30d3f7d9b78910a8bafc5f1741fee93c..b7e7388891655e8de293c4c75f2c0c67121ed547 100644
--- a/Source/core/rendering/RenderNamedFlowThread.cpp
+++ b/Source/core/rendering/RenderNamedFlowThread.cpp
@@ -47,7 +47,7 @@ namespace WebCore {
 RenderNamedFlowThread* RenderNamedFlowThread::createAnonymous(Document* document, PassRefPtr<NamedFlow> namedFlow)
 {
     ASSERT(RuntimeEnabledFeatures::cssRegionsEnabled());
-    RenderNamedFlowThread* renderer = new (document->renderArena()) RenderNamedFlowThread(namedFlow);
+    RenderNamedFlowThread* renderer = new RenderNamedFlowThread(namedFlow);
     renderer->setDocumentForAnonymous(document);
     return renderer;
 }