Update CSS tests to revision 31d63cc79bd4c929ed582229e936d7b389f3e6ab

tests/wpt/css-tests/css-backgrounds-3_dev/xhtml1/support/diagonal-scaled.svg

@@ -0,0 +1,20 @@
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+--><svg xmlns="http://www.w3.org/2000/svg">
+  <title>Vector image without intrinsic dimensions with percentage stroke-width (proportional to the diagonal)</title>
+  <rect y="0" width="100%" height="50%" fill="lime"/>
+  <rect y="50%" width="100%" height="50%" fill="aqua"/>
+  <!--
+    A percent stroke-width is resolved with respect to:
+
+      d = sqrt(vh**2 + vw**2) / sqrt(2)
+
+    where vh/vw are the image viewport width/height.  Because this image has no
+    intrinsic dimensions or ratio, it expands to fill the entire background
+    positioning area, so its width is 100px and its height is 700px.  For those
+    carefully-chosen dimensions, d = 500px, so 10% of that creates a 50px-wide
+    rectangle, vertically centered and horizontally left-aligned in the image.
+  -->
+  <line x1="25%" y1="25%" x2="25%" y2="75%" stroke="fuchsia" stroke-width="10%"/>
+</svg>