Change package scheduled_test to throw TestFailures rather than strings.

pkg/scheduled_test/test/scheduled_process_test.dart

Index: pkg/scheduled_test/test/scheduled_process_test.dart
diff --git a/pkg/scheduled_test/test/scheduled_process_test.dart b/pkg/scheduled_test/test/scheduled_process_test.dart
index 5aaae605fedc1a9ee52dc9754f6985e47b4bcb7f..3a9872c19df7a5368ea249a0cab6f83dabb6ebaf 100644
--- a/pkg/scheduled_test/test/scheduled_process_test.dart
+++ b/pkg/scheduled_test/test/scheduled_process_test.dart
@@ -143,7 +143,8 @@ void main() {
       // Whether or not this error appears depends on how quickly the "no
       // elements" error is handled.
       if (errors.length == 2) {
-        expect(errors[1].error, matches(r"^Process "
+        expect(errors[1].error, new isInstanceOf<TestFailure>());
+        expect(errors[1].error.message, matches(r"^Process "
             r"'[^']+[\\/]dart(\.exe)? [^']+' ended earlier than scheduled with "
             r"exit code 0\."));
       }
@@ -196,7 +197,8 @@ void main() {
       // Whether or not this error appears depends on how quickly the "no
       // elements" error is handled.
       if (errors.length == 2) {
-        expect(errors[1].error, matches(r"^Process "
+        expect(errors[1].error, new isInstanceOf<TestFailure>());
+        expect(errors[1].error.message, matches(r"^Process "
             r"'[^']+[\\/]dart(\.exe)? [^']+' ended earlier than scheduled with "
             r"exit code 0\."));
       }
@@ -240,7 +242,8 @@ void main() {
       // Whether or not this error appears depends on how quickly the "no
       // elements" error is handled.
       if (errors.length == 2) {
-        expect(errors[1].error, matches(r"^Process "
+        expect(errors[1].error, new isInstanceOf<TestFailure>());
+        expect(errors[1].error.message, matches(r"^Process "
             r"'[^']+[\\/]dart(\.exe)? [^']+' ended earlier than scheduled with "
             r"exit code 0\."));
       }