Don't consider controller.addError to be a zone-crossing.

tests/lib/async/catch_errors23_test.dart

Index: tests/lib/async/catch_errors23_test.dart
diff --git a/tests/lib/async/catch_errors23_test.dart b/tests/lib/async/catch_errors23_test.dart
index 7cf5294e4077007f80faded1f7b92778a628529e..898d4858f2264257f0b25b300192f4266d69c27d 100644
--- a/tests/lib/async/catch_errors23_test.dart
+++ b/tests/lib/async/catch_errors23_test.dart
@@ -33,13 +33,14 @@ main() {
       .asFuture().then((_) { Expect.fail("Unexpected callback"); });
     stream.listen((x) { events.add("stream2 $x"); });
     controller.add(1);
-    // Errors are not allowed to traverse boundaries. This error should be
-    // caught by the outer catchErrors.
-    controller.addError(2);
+    // `addError` does not count as zone-traversal. It should be caught by
+    // the inner error handler.
+    controller.addError("inner error");
+    new Future.error("caught by outer");
     controller.close();
   }).listen((x) {
                   events.add("outer: $x");
-                  if (x == 2) done.complete(true);
+                  if (x == "caught by outer") done.complete(true);
                 },
             onDone: () { Expect.fail("Unexpected callback"); });
 
@@ -47,9 +48,11 @@ main() {
     // Give handlers time to run.
     Timer.run(() {
       Expect.listEquals(["map 1",
-                        "stream 101",
-                        "stream2 101",
-                        "outer: 2",
+                         "stream 101",
+                         "stream2 101",
+                         "stream error inner error",
+                         "stream2 error inner error",
+                         "outer: caught by outer",
                         ],
                         events);
       asyncEnd();