ScrollTopLeftInterop should not be marked experimental

LayoutTests/rubberbanding/scroll-bounce-fix.html

Index: LayoutTests/rubberbanding/scroll-bounce-fix.html
diff --git a/LayoutTests/rubberbanding/scroll-bounce-fix.html b/LayoutTests/rubberbanding/scroll-bounce-fix.html
index 1c5e9a024d003ad8b134b05a08ef87ade394d99e..36c9ed51a6536db754eecbde264ab29951ea01d1 100644
--- a/LayoutTests/rubberbanding/scroll-bounce-fix.html
+++ b/LayoutTests/rubberbanding/scroll-bounce-fix.html
@@ -73,12 +73,12 @@
         setTimeout(function() {
             document.getElementById('box').style.background = 'green';
             // The left margin should have rebounded back to 0.
-            if (document.documentElement.scrollLeft != 0) {
+            if (document.body.scrollLeft != 0) {
                 document.getElementById('box').style.background = 'yellow';
             }
             // The content should be scrolled to the bottom.
             var expectedScrollTop = document.documentElement.scrollHeight - document.documentElement.clientHeight;
-            if (document.documentElement.scrollTop != expectedScrollTop) {
+            if (document.body.scrollTop != expectedScrollTop) {
                 document.getElementById('box').style.background = 'yellow';
             }
             testRunner.notifyDone();