Reapply the non-MathExtras parts of

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 645 matching lines @@
     }
 
     return 0;
 }
 
 void Element::setScrollLeft(double newLeft)
 {
     document().updateLayoutIgnorePendingStylesheets();
 
     if (document().documentElement() != this) {
-        if (RenderBox* rend = renderBox())
+        RenderBox* rend = renderBox();
+        if (rend && !std::isnan(newLeft))
             rend->setScrollLeft(LayoutUnit::fromFloatRound(newLeft * rend->style()->effectiveZoom()));
         return;
     }
 
     if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
         if (document().inQuirksMode())
             return;
 
         LocalFrame* frame = document().frame();
         if (!frame)
@@ skipping 25 matching lines @@
 
     // FIXME: Use scrollBehavior to decide whether to scroll smoothly or instantly.
     setScrollLeft(position);
 }
 
 void Element::setScrollTop(double newTop)
 {
     document().updateLayoutIgnorePendingStylesheets();
 
     if (document().documentElement() != this) {
-        if (RenderBox* rend = renderBox())
+        RenderBox* rend = renderBox();
+        if (rend && !std::isnan(newTop))
             rend->setScrollTop(LayoutUnit::fromFloatRound(newTop * rend->style()->effectiveZoom()));
         return;
     }
 
     if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {
         if (document().inQuirksMode())
             return;
 
         LocalFrame* frame = document().frame();
         if (!frame)
@@ skipping 2539 matching lines @@
         return wrapper;
 
     CustomElementBinding* binding = perContextData->customElementBinding(customElementDefinition());
 
     wrapper->SetPrototype(binding->prototype());
 
     return V8DOMWrapper::associateObjectWithWrapperNonTemplate(this, wrapperType, wrapper, isolate);
 }
 
 } // namespace blink