Add test for bug 620428 (setinterval cancellation)

testing/resources/bug_620428.in

Index: testing/resources/bug_620428.in
diff --git a/testing/resources/bug_551248.in b/testing/resources/bug_620428.in
similarity index 80%
copy from testing/resources/bug_551248.in
copy to testing/resources/bug_620428.in
index ad10e93912cb2323ded1665b4de5f8aafab5e0b5..1942305173c3c9166f3cadfb75d33941322b23ff 100644
--- a/testing/resources/bug_551248.in
+++ b/testing/resources/bug_620428.in
@@ -65,11 +65,16 @@ endobj
 {{object 50 0}} <<
 >>
 stream
-function startDelay()
-{
+function fireTimeOut() {
   app.alert("hello world");
 }
-app.setTimeOut("startDelay()", 3000);
+function fireInterval() {
+  app.alert("goodbye world");
+}
+var timer = app.setTimeOut("fireTimeOut()", 3000);
+var interval = app.setInterval("fireInterval()", 1000);
+app.clearTimeOut(timer);
+app.clearInterval(interval);
 endstream
 endobj
 {{xref}}