clear mapped values if we're not animating any more

Differential Revision: https://phabricator.services.mozilla.com/D188712

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1717312
gecko-commit: 8c1de03e7bef70e1608360c839c4ec9669f48902
gecko-reviewers: emilio
diff --git a/svg/animations/scripted/clear-mapped-animation.svg b/svg/animations/scripted/clear-mapped-animation.svg
new file mode 100644
index 0000000..518fe61
--- /dev/null
+++ b/svg/animations/scripted/clear-mapped-animation.svg
@@ -0,0 +1,17 @@
+<svg class="reftest-wait" onload="load()" xmlns="http://www.w3.org/2000/svg"
+  xmlns:html="http://www.w3.org/1999/xhtml">
+  <html:link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1717312"/>
+  <html:script src="/common/reftest-wait.js"/>
+  <html:script src="/common/rendering-utils.js"/>
+  <html:link rel="match" href="../../embedded/reference/green-rect-100x100.svg"/>
+  <rect id="r" width="100" height="50" fill="green">
+    <animate attributeName="height" values="0" dur="20ms"/>
+  </rect>
+  <script>
+    function load() {
+      document.documentElement.setCurrentTime(1);
+      document.getElementById("r").setAttribute("height", 100);
+      waitForAtLeastOneFrame().then(takeScreenshot);
+    }
+  </script>
+</svg>