Fix improper scrollTop/Left usage in LayoutTests/

LayoutTests/editing/input/resources/reveal-utilities.js

 function offsetFromViewportTop(element)
 {
     return element.getClientRects()[0].top;
 }
 
 function offsetOfMiddleFromViewportTop(element)
 {
     return element.getClientRects()[0].top + Math.round(element.getClientRects()[0].height / 2);
 }
 
@@ skipping 55 matching lines @@
 }
 
 function performJumpAtTheEdgeTest(useCtrlKeyModifier)
 {
     var textArea = document.getElementById("input");
     textArea.focus();
     if (window.eventSender) {
         var previousScrollTop = 0, currentScrollTop = 0;
         var jumpDetected = false;
         for (var i = 0; i < 120; ++i) {
-            previousScrollTop = document.body.scrollTop;
+            previousScrollTop = document.documentElement.scrollTop;
             eventSender.keyDown("\r", useCtrlKeyModifier ? ["ctrlKey"] : []);
-            currentScrollTop = document.body.scrollTop;
+            currentScrollTop = document.documentElement.scrollTop;
             // Smooth scrolls are allowed.
             if (Math.abs(previousScrollTop - currentScrollTop) > 24) {
                 jumpDetected = true;
                 break;
             }
         }
         if (!jumpDetected)
             document.write("PASS");
         else
             document.write("FAIL<br>Jump scroll from " + previousScrollTop + " to " + currentScrollTop);
     }
 }