Fix static type warnings in test.dart.

client/tests/dartc/test_config.dart

Index: client/tests/dartc/test_config.dart
diff --git a/client/tests/dartc/test_config.dart b/client/tests/dartc/test_config.dart
index b666ee3ec3ba2745aecf90cdced942bd20e6b6d7..180ca03511c5d5d3658cb62b563dd5343eca5e20 100644
--- a/client/tests/dartc/test_config.dart
+++ b/client/tests/dartc/test_config.dart
@@ -27,11 +27,11 @@ class ClientDartcTestSuite extends DartcCompilationTestSuite {
                'weld'],
               ["client/tests/dartc/dartc.status"]);
 
-  void isTestFile(String filename) {
+  bool isTestFile(String filename) {
     if (!filename.endsWith(".dart")) return false;
     var options = optionsFromFile(filename);
     return optionsFromFile(filename)["containsLeadingHash"];
   }
 
-  void listRecursively() => true;
+  bool listRecursively() => true;
 }