Avoid N^2 walk placing renderers when building the render tree

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index a3ab8ce1826bf37261143e4304a5c70b3bf835ac..64eb17f3cc967313777ea551da09259b6140a1e7 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -1120,6 +1120,16 @@ void Node::detach(const AttachContext& context)
 #endif
 }
 
+void Node::reattachWhitespaceSiblings() const
+{
+    for (Node* sibling = nextSibling(); sibling; sibling = sibling->nextSibling()) {
+        if (sibling->renderer())
+            return;
+        if (sibling->isTextNode() && toText(sibling)->containsOnlyWhitespace())
+            sibling->reattach();
+    }
+}
+
 // FIXME: This code is used by editing.  Seems like it could move over there and not pollute Node.
 Node *Node::previousNodeConsideringAtomicNodes() const
 {