Perf bots for https://codereview.chromium.org/2473743003

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 2041 matching lines @@
   StyleResolver& resolver = ensureStyleResolver();
 
   bool shouldRecordStats;
   TRACE_EVENT_CATEGORY_GROUP_ENABLED("blink,blink_style", &shouldRecordStats);
   styleEngine().setStatsEnabled(shouldRecordStats);
 
   if (Element* documentElement = this->documentElement()) {
     inheritHtmlAndBodyElementStyles(change);
     if (documentElement->shouldCallRecalcStyle(change))
       documentElement->recalcStyle(change);
+    if (documentElement->needsReattachLayoutTree() ||
+        documentElement->childNeedsReattachLayoutTree())
+      documentElement->rebuildLayoutTree();
   }
 
   view()->recalcOverflowAfterStyleChange();
 
   // Only retain the HashMap for the duration of StyleRecalc and
   // LayoutTreeConstruction.
   m_styleReattachDataMap.clear();
   clearChildNeedsStyleRecalc();
   clearChildNeedsReattachLayoutTree();
 
@@ skipping 4526 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (blink::Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif