Reland main thread position sticky implementation.

third_party/WebKit/LayoutTests/fast/css/sticky/overflow-layer-removed-crash.html

Index: third_party/WebKit/LayoutTests/fast/css/sticky/overflow-layer-removed-crash.html
diff --git a/third_party/WebKit/LayoutTests/fast/css/sticky/overflow-layer-removed-crash.html b/third_party/WebKit/LayoutTests/fast/css/sticky/overflow-layer-removed-crash.html
new file mode 100644
index 0000000000000000000000000000000000000000..0a474d772313eb39befaad3f8542313b8b16a352
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/css/sticky/overflow-layer-removed-crash.html
@@ -0,0 +1,34 @@
+<style>
+.scroll {
+    overflow: hidden;
+}
+
+.layer {
+    will-change: transform;
+}
+</style>
+<script>
+if (window.testRunner) {
+    testRunner.dumpAsText();
+    testRunner.waitUntilDone();
+}
+
+function crash() {
+    document.getElementById('scroll').classList.remove('scroll');
+    document.getElementById('scroll').classList.remove('layer');
+    document.getElementById('layer').classList.remove('layer');
+    if (window.testRunner)
+        testRunner.notifyDone();
+}
+
+window.onload = function() {
+    // Call crash after 2 rafs.
+    requestAnimationFrame(requestAnimationFrame.bind(null, crash));
+}
+</script>
+<p>This test PASSES if it does not CRASH.</p>
+<div id="scroll" class="scroll layer">
+    <div class="layer">
+        <div id="layer" class="layer"></div>
+    </div>
+</div>