Handle nested position:sticky elements

third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table-expected.html

Index: third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table-expected.html
diff --git a/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table-expected.html b/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table-expected.html
new file mode 100644
index 0000000000000000000000000000000000000000..fae12b365cb51fa1edcb843734264f878fc43cf9
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table-expected.html
@@ -0,0 +1,50 @@
+<style>
+body {
+  margin: 0;
+}
+
+table {
+  background: red;
+  border-collapse: collapse;
+}
+
+td, th {
+  height: 50px;
+  width: 50px;
+  padding: 0;
+}
+
+th {
+  position: absolute;
+  top: 25px;
+  background: green;
+}
+
+.container {
+  overflow: hidden;
+  width: 100px;
+  height: 200px;
+  outline: 2px solid black;
+}
+</style>
+
+<div class="container">
+  <table>
+    <thead class="sticky">
+      <tr class="sticky">
+        <th class="sticky"></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>
+    </tbody>
+  </table>
+</div>