Beef up timer cancellation tests

testing/resources/bug_620428.pdf

Index: testing/resources/bug_620428.pdf
diff --git a/testing/resources/bug_620428.pdf b/testing/resources/bug_620428.pdf
index ff625b7a2e387d4a2d67b1b14a2667bc18466075..e53ed50e24bf811c8b476c964b0249ae9473a0e5 100644
--- a/testing/resources/bug_620428.pdf
+++ b/testing/resources/bug_620428.pdf
@@ -74,8 +74,22 @@ function fireInterval() {
 }
 var timer = app.setTimeOut("fireTimeOut()", 3000);
 var interval = app.setInterval("fireInterval()", 1000);
+// Clear timers before they fire.
 app.clearTimeOut(timer);
 app.clearInterval(interval);
+// Check that clearing a cleared timer is ok.
+app.clearTimeOut(timer);
+app.clearInterval(interval);
+// Check that invoking the wrong clear method is ok
+var timer = app.setTimeOut("fireTimeOut()", 3000);
+var interval = app.setInterval("fireInterval()", 1000);
+app.clearTimeOut(interval);
+app.clearInterval(timer);
+// Check that clearing a non-timer is ok.
+app.clearTimeOut({"size": 42});
+app.clearInterval({"size": 42});
+// Be sure all of this code ran to completion.
+app.alert("done");
 endstream
 endobj
 xref
@@ -135,5 +149,5 @@ trailer <<
   /Root 1 0 R
 >>
 startxref
-1135
+1655
 %%EOF