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diff --git a/layout/reftests/border-radius/curved-border-background-nogap.html b/layout/reftests/border-radius/curved-border-background-nogap.html
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+++ b/layout/reftests/border-radius/curved-border-background-nogap.html
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+<!DOCTYPE html>
+<style>
+  /*
+    Turns out that the antialiasing on the outer edge of a block with
+    border-radius is not consistent if the width and border-width are changed
+    even if the resulting shape should look the same.  So clip out the part
+    that's too far from the center
+  */
+  div.outer {
+    width: 100px;
+    height: 100px;
+    overflow: hidden;
+  }
+  /* We want the following constraints to be satisfied:
+     1)  Entire inner div content area is contained inside the 100px square.
+     2)  Entire 100px square is contained inside the outer circle of the inner
+         div's border.
+
+     This requires that the inner div width/height be < 100px and that the
+     radius of the outer circle be at least 50 * sqrt(2).  Let's go with a 75px
+     radius for that outer circle.  We then need to shift our inner div up and
+     to the left by 25px to center it in the clipping region.
+    */
+
+  div.inner {
+    width: 50px;
+    height: 50px;
+    border: 50px solid black;
+    background: black;
+    border-radius: 100px;
+    position: relative;
+    top: -25px;
+    left: -25px;
+  }
+</style>
+<div class="outer"><div class="inner"></div></div>