Isolate.spawn{Uri} only reports errors asynchronously.

tests/isolate/static_function_test.dart

Index: tests/isolate/static_function_test.dart
diff --git a/tests/isolate/static_function_test.dart b/tests/isolate/static_function_test.dart
index db0beba16763cff1abccfd1b02a09e9430685042..afa52bddc3f86e22f73df51891f9ee0b1d44a666 100644
--- a/tests/isolate/static_function_test.dart
+++ b/tests/isolate/static_function_test.dart
@@ -72,7 +72,9 @@ void spawnTest(name, function, response) {
 
 void throwsTest(name, function) {
   test("throws on $name", () {
-    expect(() { Isolate.spawn(function, null); }, throws);
+    Isolate.spawn(function, null).catchError(expectAsync1((e) {
+      /* do nothing */
+    }));
   });
 }