Add test for bug 620428 (setinterval cancellation)

testing/resources/bug_551248.pdf

Index: testing/resources/bug_551248.pdf
diff --git a/testing/resources/bug_551248.pdf b/testing/resources/bug_551248.pdf
index cca1872ee7679be24520da251703bd62784af1c2..dea541a8de7344477c6af48229ff2f31354f718d 100644
--- a/testing/resources/bug_551248.pdf
+++ b/testing/resources/bug_551248.pdf
@@ -66,11 +66,14 @@ endobj
 50 0 obj <<
 >>
 stream
-function startDelay()
-{
-  app.alert("hello world");
+function fireTimeOut() {
+  app.alert("timer fired");
 }
-app.setTimeOut("startDelay()", 3000);
+function fireInterval() {
+  app.alert("interval fired");
+}
+app.setTimeOut("fireTimeOut()", 3000);
+app.setInterval("fireInterval()", 2000);
 endstream
 endobj
 xref
@@ -130,5 +133,5 @@ trailer <<
   /Root 1 0 R
 >>
 startxref
-954
+1055
 %%EOF