Handle nested position:sticky elements

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

Index: third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table.html
diff --git a/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table.html b/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table.html
new file mode 100644
index 0000000000000000000000000000000000000000..79d2df2cd04387c00f73c98c4f972fddb8dd608c
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/compositing/overflow/composited-nested-sticky-table.html
@@ -0,0 +1,82 @@
+<script>
+if (window.testRunner)
+  testRunner.waitUntilDone();
+
+function doTest() {
+  finishTestInXFrames(2);
+}
+
+function finishTestInXFrames(frames) {
+  if (frames > 0) {
+    requestAnimationFrame(finishTestInXFrames.bind(null, frames - 1));
+    return;
+  }
+  finishTest();
+}
+
+function finishTest() {
+  document.querySelector('.scroller').scrollTop = 200;
+  if (window.testRunner)
+    testRunner.notifyDone();
+}
+
+window.addEventListener('load', doTest, false);
+</script>
+
+<style>
+body {
+  margin: 0;
+}
+
+table {
+  will-change: transform;
+
+  background: red;
+  border-collapse: collapse;
+}
+
+td, th {
+  height: 50px;
+  width: 50px;
+  padding: 0;
+}
+
+th {
+  background: green;
+}
+
+.scroller {
+  will-change: transform;
+
+  overflow: hidden; /* hide scrollbars */
+  width: 100px;
+  height: 200px;
+  outline: 2px solid black;
+}
+
+.sticky {
+  position: sticky;
+  top: 25px;
+}
+</style>
+
+<div class="scroller">
+  <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>