ScrollTopLeftInterop should not be marked experimental

LayoutTests/compositing/scissor-out-of-viewport.html

Index: LayoutTests/compositing/scissor-out-of-viewport.html
diff --git a/LayoutTests/compositing/scissor-out-of-viewport.html b/LayoutTests/compositing/scissor-out-of-viewport.html
index 5c46a961858fefa43dc40c24ee5a35ad5e21e928..d3e4e830d9c8ef5b3fc0f2e328693757e9c40832 100644
--- a/LayoutTests/compositing/scissor-out-of-viewport.html
+++ b/LayoutTests/compositing/scissor-out-of-viewport.html
@@ -18,7 +18,7 @@ var ctx = can.getContext("2d");
 ctx.fillStyle = "red";
 ctx.fillRect(0, 0, 500, 500);
 document.getElementById("i").src = can.toDataURL();
-document.documentElement.scrollTop = 50;
+document.body.scrollTop = 50;
 if (window.testRunner)
     testRunner.dumpAsTextWithPixelResults();
 </script>