Option to disable message widget

lib/src/testing.dart

Index: lib/src/testing.dart
diff --git a/lib/src/testing.dart b/lib/src/testing.dart
index 81c25e304c7f6aa6e78339cf8a1b3c532157c691..8ad61311fe2c6b754cd53034cb30d495cdf56416 100644
--- a/lib/src/testing.dart
+++ b/lib/src/testing.dart
@@ -94,7 +94,7 @@ void testChecker(Map<String, String> testFiles, {String sdkDir,
 MemoryResourceProvider createTestResourceProvider(
     Map<String, String> testFiles) {
   var provider = new MemoryResourceProvider();
-  runtimeFilesForServerMode.forEach((filepath) {
+  runtimeFilesForServerMode().forEach((filepath) {
     testFiles['/dev_compiler_runtime/$filepath'] =
         '/* test contents of $filepath */';
   });