Update most LayoutTests to be agnostic to scrollTopLeftInterop mode

LayoutTests/fast/events/scroll-in-scaled-page-with-overflow-hidden.html

 <style>
     html, body { margin:0; overflow: hidden; }
 </style>
 <script src="../../resources/js-test.js"></script>
 
 <div>
   This tests that a usually overflow: hidden viewport should be scrollable when
   scaled. Otherwise, you can't get to content you would have been able to get to
   had you not been zoomed it.
 </div>
 <div id="console"></div>
 
 <div style='font-size:40px; height: 1000px;'>
 </div>
 
 <script>
     (function() {
         if (!window.testRunner) {
             debug("This test only works in the test runner.");
             return;
         }
 
         // Force a layout.
         document.body.offsetLeft;
 
         if (window.eventSender)
             window.eventSender.setPageScaleFactor(2, 0, 0);
 
-        shouldBe("window.document.body.scrollTop", "0");
+        // Note that with ScrollTopLeftInterop enabled, document.scrollingElement is
+        // null because body is potentially scrollable (with overflow:hidden the 
+        // box can still be scrolled progamatically).

[tdresser, 2015/05/19 13:53:11]

progamatically -> programmatically 
body -> document.body

[Rick Byers, 2015/05/20 15:10:24]

Done.

+        shouldBe("window.scrollY", "0");
 
         if (window.eventSender) {
             eventSender.mouseMoveTo(100, 100);
             eventSender.mouseScrollBy(0, -5);
         }
 
-        shouldBe("window.document.body.scrollTop", "200");
+        shouldBe("window.scrollY", "200");
     })();
 </script>