Reapply the non-MathExtras parts of

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index 3fbc3c43508309278c1bade06826703856a2de2e..a3807aec2b78bdc81ec01a43bcb432c81df92be3 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -663,7 +663,8 @@ 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;
     }
@@ -709,7 +710,8 @@ 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;
     }