Repair a dart2js test failure due to unused methods.

tests/compiler/dart2js/analyze_unused_dart2js_test.dart

Index: tests/compiler/dart2js/analyze_unused_dart2js_test.dart
diff --git a/tests/compiler/dart2js/analyze_unused_dart2js_test.dart b/tests/compiler/dart2js/analyze_unused_dart2js_test.dart
index b1eaf6e168316cab9a2801ac57502964375bb7fe..1ba1caba15ce19ee3e9a7845ffbd6b25da074274 100644
--- a/tests/compiler/dart2js/analyze_unused_dart2js_test.dart
+++ b/tests/compiler/dart2js/analyze_unused_dart2js_test.dart
@@ -52,9 +52,16 @@ const Map<String, List<String>> WHITE_LIST = const {
     "accept", "CreateFunction",
   ],
 
-  "/lib/src/dart_backend/backend_ast_to_frontend_ast.dart": const [
+  "lib/src/dart_backend/backend_ast_to_frontend_ast.dart": const [
     " is never "
   ],
+
+  // Useful utility functions that are not currently used.
+  "lib/src/cps_ir/cps_fragment.dart": const [
+    "The method 'beginLoop' is never called.",
+    "The method 'continueLoop' is never called.",
+    "The method 'invokeMethod' is never called.",
+  ],
 };
 
 void main() {