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Test Info:
<!DOCTYPE html>
<html lang="en">
<meta charset="utf-8">
<title>The two items in the scroll box should share a layer, despite all the other stuff that's going on around them</title>
<style>
.content {
box-sizing: border-box;
width: 200px;
height: 200px;
border: 1px solid blue;
background: white;
}
body {
margin: 0;
padding: 20px;
height: 3000px;
}
.opacity {
opacity: 0.9;
width: 200px;
height: 200px;
background-color: yellow;
will-change: opacity;
}
.overlap {
margin-top: -100px;
}
.scrollable {
position: absolute;
top: 20px;
left: 240px;
width: 400px;
height: 400px;
border: 1px solid black;
overflow: auto;
}
.scrollarea {
height: 800px;
padding: 40px;
}
.low-z, .mid-z, .high-z {
position: relative;
}
.low-z { z-index: 1; }
.mid-z { z-index: 2; }
.high-z { z-index: 3; }
</style>
<div class="content" reftest-assigned-layer="page-background"></div>
<div class="overlap opacity"></div>
<div class="overlap mid-z content" reftest-assigned-layer="on-top-of-opacity">
<!--
This item cannot merge into the page background layer because there's an
active container layer for the opacity in between.
-->
</div>
<div class="scrollable">
<div class="scrollarea">
<div class="low-z content" reftest-assigned-layer="scrolled-content"></div>
<div class="high-z overlap content" reftest-assigned-layer="scrolled-content"></div>
</div>
</div>
<script>
var scrollable = document.querySelector(".scrollable");
// Make .scrollable start out with active scrolling.
scrollable.scrollTop = 0;
scrollable.scrollTop = 20;
</script>