Make catch_errors13_test non-flaky.

tests/lib/async/catch_errors13_test.dart

Index: tests/lib/async/catch_errors13_test.dart
diff --git a/tests/lib/async/catch_errors13_test.dart b/tests/lib/async/catch_errors13_test.dart
index 0889f2e19340878fa3facd825b97276f41e74842..73f52e3bd71f7cfe21518e91ec6283179aa80e96 100644
--- a/tests/lib/async/catch_errors13_test.dart
+++ b/tests/lib/async/catch_errors13_test.dart
@@ -19,16 +19,28 @@ main() {
 
   // Test that errors are caught by nested `catchErrors`. Also uses
   // `scheduleMicrotask` in the body of a Timer.
+  bool outerTimerRan = false;
+  int outerTimerCounterDelayCount = 0;
   catchErrors(() {
     events.add("catch error entry");
     catchErrors(() {
       events.add("catch error entry2");
       Timer.run(() { throw "timer error"; });
-      new Timer(const Duration(milliseconds: 50),
-                () {
-                     scheduleMicrotask(() { throw "scheduleMicrotask"; });
-                     throw "delayed error";
-                   });
+
+      void runDelayed() {
+        new Timer(const Duration(milliseconds: 10),
+                  () {
+                    if (outerTimerRan) {
+                      scheduleMicrotask(() { throw "scheduleMicrotask"; });
+                      throw "delayed error";
+                    } else if (outerTimerCounterDelayCount < 100) {

[sra1, 2013/11/08 00:09:02]

What is significant about "100" ?

It seems to me if the original test was slightly nondeterministic for valid
reasons, the test should check for correct nondeterministic behaviour, e.g all
errors are reported, some errors must precede others etc.

Perhaps have two tests: the new test with forced order, and the original
checking only that the set of errors is reported.

[floitsch, 2013/11/08 00:19:52]

I prefer making it deterministic. Added a comment.

+                      outerTimerCounterDelayCount++;
+                      runDelayed();
+                    }
+                  });
+      }
+
+      runDelayed();
     }).listen((x) {
       events.add(x);
       if (x == "scheduleMicrotask") {
@@ -36,7 +48,10 @@ main() {
       }
     });
     events.add("after inner");
-    Timer.run(() { throw "timer outer"; });
+    Timer.run(() {
+      outerTimerRan = true;
+      throw "timer outer";
+    });
     throw "inner throw";
   }).listen((x) {
       events.add(x);