1 files changed, 46 insertions, 0 deletions
diff --git a/gfx/layers/apz/test/mochitest/helper_scroll_inactive_zindex.html b/gfx/layers/apz/test/mochitest/helper_scroll_inactive_zindex.html
new file mode 100644
index 0000000000..44c3cf3217
--- /dev/null
+++ b/gfx/layers/apz/test/mochitest/helper_scroll_inactive_zindex.html
@@ -0,0 +1,46 @@
+<head>
+  <meta name="viewport" content="width=device-width; initial-scale=1.0">
+  <title>Wheel-scrolling over inactive subframe with z-index</title>
+  <script type="application/javascript" src="apz_test_native_event_utils.js"></script>
+  <script type="application/javascript" src="apz_test_utils.js"></script>
+  <script src="/tests/SimpleTest/paint_listener.js"></script>
+  <script type="application/javascript">
+
+async function test() {
+  var subframe = document.getElementById("scroll");
+
+  // scroll over the middle of the subframe, and make sure that it scrolls,
+  // not the page
+  var scrollPos = subframe.scrollTop;
+  await promiseMoveMouseAndScrollWheelOver(subframe, 100, 100);
+  dump("after scroll, subframe.scrollTop = " + subframe.scrollTop + "\n");
+  ok(subframe.scrollTop > scrollPos, "subframe scrolled after wheeling over it");
+}
+
+waitUntilApzStable()
+.then(test)
+.then(subtestDone, subtestFailed);
+
+  </script>
+  <style>
+    #scroll {
+      width: 200px;
+      height: 200px;
+      overflow: scroll;
+    }
+    #scrolled {
+      width: 200px;
+      height: 1000px; /* so the subframe has room to scroll */
+      z-index: 2;
+      background: linear-gradient(red, blue); /* so you can see it scroll */
+      transform: translateZ(0px); /* to force active layers */
+      will-change: transform; /* to force active layers */
+    }
+  </style>
+</head>
+<body>
+  <div id="scroll">
+    <div id="scrolled"></div>
+  </div>
+  <div style="height: 5000px;"></div><!-- So the page is scrollable as well -->
+</body>