Avoid relying on vertical scrollbar placement in a couple of tests. (#28425)

These two tests can end up placing their root vertical scrollbars on different sides of
the window, due to the use of different writing modes.  They aren't specifically testing
anything to do with scrollbars, so we turn them off.
diff --git a/css/css-writing-modes/sizing-orthog-vrl-in-htb-013-ref.xht b/css/css-writing-modes/sizing-orthog-vrl-in-htb-013-ref.xht
index f274aaf..597cac9 100644
--- a/css/css-writing-modes/sizing-orthog-vrl-in-htb-013-ref.xht
+++ b/css/css-writing-modes/sizing-orthog-vrl-in-htb-013-ref.xht
@@ -18,6 +18,8 @@
     {
       height: 100%;
       writing-mode: vertical-rl;
+      overflow: hidden; /* since test and reference might place scrollbars on
+                           different sides */
     }
 
   body
diff --git a/css/css-writing-modes/sizing-orthog-vrl-in-htb-013.xht b/css/css-writing-modes/sizing-orthog-vrl-in-htb-013.xht
index 997174e..75cf1aa 100644
--- a/css/css-writing-modes/sizing-orthog-vrl-in-htb-013.xht
+++ b/css/css-writing-modes/sizing-orthog-vrl-in-htb-013.xht
@@ -60,6 +60,12 @@
   -->
 
   <style type="text/css"><![CDATA[
+  html
+    {
+      overflow: hidden; /* since test and reference might place scrollbars on
+                           different sides */
+    }
+
   body
     {
       font-size: 16px;
diff --git a/css/cssom-view/cssom-getBoundingClientRect-vertical-rl-ref.html b/css/cssom-view/cssom-getBoundingClientRect-vertical-rl-ref.html
index 1ee4fe2..0b68c4f 100644
--- a/css/cssom-view/cssom-getBoundingClientRect-vertical-rl-ref.html
+++ b/css/cssom-view/cssom-getBoundingClientRect-vertical-rl-ref.html
@@ -1,4 +1,4 @@
 <!DOCTYPE html>
-<body style="overflow: scroll">
+<body style="overflow: hidden">
   <div style="position: absolute; top: 50px; left: 50px; width: 200px; height: 200px; background: green"></div>
 </body>
diff --git a/css/cssom-view/cssom-getBoundingClientRect-vertical-rl.html b/css/cssom-view/cssom-getBoundingClientRect-vertical-rl.html
index 85ac2a9..62f010a 100644
--- a/css/cssom-view/cssom-getBoundingClientRect-vertical-rl.html
+++ b/css/cssom-view/cssom-getBoundingClientRect-vertical-rl.html
@@ -3,7 +3,7 @@
 <link rel="help" href="http://www.w3.org/TR/cssom-view/#dom-element-getboundingclientrect">
 <link rel=match href="cssom-getBoundingClientRect-vertical-rl-ref.html">
 <meta name="flags" content="dom">
-<body style="writing-mode: vertical-rl; overflow: scroll">
+<body style="writing-mode: vertical-rl; overflow: hidden">
   <div id="target" style="position: absolute; top: 50px; left: 50px; width: 200px; height: 200px; background: red"></div>
   <div id="overlay" style="position: absolute; background: green"></div>
   <script>