Enable position:sticky for <thead> and <tr> elements

third_party/WebKit/LayoutTests/fast/css/sticky/sticky-table-thead-multirow-top.html

 <style>
-body {
-  margin: 0;
-}
 
 table {
-  background: red;
   border-collapse: collapse;
 }
 
 td, th {
-  height: 50px;
-  width: 50px;
-  padding: 0;
+  height: 40px;
+  width: 40px;
 }
 
 th {
   background: green;
 }
 
 .scroller {
-  overflow: hidden; /* hide scrollbars */
-  width: 100px;
-  height: 200px;
-  outline: 2px solid black;
+  overflow: auto;
+  height: 400px;
 }
 
 .sticky {
   position: sticky;
   top: 25px;
 }
+
+.padding {
+  height: 500px;
+}
 </style>
 
 <script>
 if (window.testRunner)
   testRunner.waitUntilDone();
 
 function finishTest() {
   document.querySelector('.scroller').scrollTop = 200;
   if (window.testRunner)
     testRunner.notifyDone();
 }
 
 window.addEventListener('load', function() {
   requestAnimationFrame(function() {
     requestAnimationFrame(finishTest);
   });
 });
 </script>
 
 <div class="scroller">
+
   <table>
     <thead class="sticky">
-      <tr class="sticky">
-        <th class="sticky"></th>
+      <tr>
+        <th rowspan="2"></th>
+        <th></th>
+      </tr>
+      <tr>
+        <th style="background: fuchsia;"></th>
       </tr>
     </thead>
     <tbody>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
-      <tr><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
+      <tr><td></td><td></td></tr>
     </tbody>
-  </table>
+    </table>
+
+  <div class="padding"></div>
+
 </div>