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diff --git a/layout/reftests/async-scrolling/overscroll-subframe.html b/layout/reftests/async-scrolling/overscroll-subframe.html
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+++ b/layout/reftests/async-scrolling/overscroll-subframe.html
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+<!DOCTYPE html>
+<html reftest-async-scroll>
+<head>
+  <style>
+    * {
+      scrollbar-width: none;
+    }
+    body {
+      margin: 0;
+    }
+    #scroller {
+      overflow: auto;
+      width: 400px;
+      height: 400px;
+    }
+    #content {
+      top: 0px;
+      width: 200px;
+      height: 200px;
+      background: green;
+    }
+    #spacer {
+      height: 2000px;
+    }
+  </style>
+</head>
+<body >
+  <!-- Test that an overscroll past one end of a viewport is rendered
+      as having the content create a gutter, and that
+      the overscroll is reduced by some factor such that 
+      a 100px scroll must produce a rendered translation of less than
+      100px.
+
+      Current overscroll physics mean that an instantaneous overscroll
+      by 200px produces an 8px gutter. This is governed by the logic in
+      Axis::ApplyResistance(); if that logic is changed, this test will
+      need to be modified to account for the new result.
+  -->
+  <div id="scroller"
+       reftest-displayport-x="0" reftest-displayport-y="0"
+       reftest-displayport-w="800" reftest-displayport-h="2000"
+       reftest-async-scroll-x="0" reftest-async-scroll-y="-200">
+    <div id="content"></div>
+    <div id="spacer"></div>
+  </div>
+</body>
+</html>