Add early out back to Node::updateDistribution().

Source/core/dom/Node.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 635 matching lines @@
 
 #if ENABLE(ASSERT)
 bool Node::needsDistributionRecalc() const
 {
     return rootInTreeOfTrees(*this).childNeedsDistributionRecalc();
 }
 #endif
 
 void Node::updateDistribution()
 {
+    // Extra early out to avoid spamming traces.
+    if (inDocument() && !document().childNeedsDistributionRecalc())
+        return;
     TRACE_EVENT0("blink", "Node::updateDistribution");
     ScriptForbiddenScope forbidScript;
-    rootInTreeOfTrees(*this).recalcDistribution();
+    Node& root = rootInTreeOfTrees(*this);
+    if (root.childNeedsDistributionRecalc())
+        root.recalcDistribution();
 }
 
 void Node::recalcDistribution()
 {
+    ASSERT(childNeedsDistributionRecalc());
+
     if (isElementNode()) {
         if (ElementShadow* shadow = toElement(this)->shadow())
             shadow->distributeIfNeeded();
     }
 
     for (Node* child = firstChild(); child; child = child->nextSibling()) {
         if (child->childNeedsDistributionRecalc())
             child->recalcDistribution();
     }
 
@@ skipping 1718 matching lines @@
 
 void showNodePath(const blink::Node* node)
 {
     if (node)
         node->showNodePathForThis();
     else
         fprintf(stderr, "Cannot showNodePath for (nil)\n");
 }
 
 #endif