ScrollTopLeftInterop should not be marked experimental

LayoutTests/fast/dom/anchor-without-content.html

Index: LayoutTests/fast/dom/anchor-without-content.html
diff --git a/LayoutTests/fast/dom/anchor-without-content.html b/LayoutTests/fast/dom/anchor-without-content.html
index b08893d5d15baddb845b1c8d0df1f16c816bf09a..caa9cdf3b39477422a83b9489435bf3745e1ab8c 100644
--- a/LayoutTests/fast/dom/anchor-without-content.html
+++ b/LayoutTests/fast/dom/anchor-without-content.html
@@ -25,16 +25,16 @@
         <span class="spacer"></span>
         
         <script>
-            var scrollTopBeforeClick = document.documentElement.scrollTop;
+            var scrollTopBeforeClick = document.body.scrollTop;
             document.getElementById('goto-1').click();
-            if (document.documentElement.scrollTop > scrollTopBeforeClick)
+            if (document.body.scrollTop > scrollTopBeforeClick)
                 testPassed('Clicking link 1 scrolled to block 1.');
             else
                 testFailed('Clicking link 1 didn\'t scroll as expected.');
                 
-            var scrollTopBeforeClick = document.documentElement.scrollTop;
+            var scrollTopBeforeClick = document.body.scrollTop;
             document.getElementById('goto-2').click();
-            if (document.documentElement.scrollTop > scrollTopBeforeClick)
+            if (document.body.scrollTop > scrollTopBeforeClick)
                 testPassed('Clicking link 2 scrolled to block 2.');
             else
                 testFailed('Clicking link 2 didn\'t scroll as expected.');