Improve handling of intentionally broken links in test scripts.

tests/_chrome/sample_test.dart

Index: tests/_chrome/sample_test.dart
diff --git a/tests/_chrome/sample_test.dart b/tests/_chrome/sample_test.dart
index 85448ff43768660905a844737ea8af01f7b883ec..b25a94b9b3ffb7c26efad219f0dfbd4552315eeb 100644
--- a/tests/_chrome/sample_test.dart
+++ b/tests/_chrome/sample_test.dart
@@ -17,7 +17,7 @@ main() {
   test('fails from browser', () {
     // APIs should not work in standard browser apps.
     expect(() {
-      _chrome.app.window.create('foo.html');
+      _chrome.app.window.create('IntentionallyMissingFile.html');
     }, throws);
   });
 }