Add access the Message in CompilerDiagnostics.report.

tests/compiler/dart2js/import_mirrors_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Test that the compiler emits a warning on import of 'dart:mirrors' unless
 // the flag --enable-experimental-mirrors is used.
 
 library dart2js.test.import;
 
 import 'dart:async';
@@ skipping 324 matching lines @@
   'paths':
       "first.dart => package:packagename => dart:mirrors",
   'verbosePaths':
       "main.dart => first.dart => package:packagename/second.dart "
       "=> dart:mirrors",
 };
 
 Future test(Map sourceFiles,
             {expectedPaths,
              bool verbose: false,
-             bool enableExperimentalMirrors: false}) {
+             bool enableExperimentalMirrors: false}) async {
   if (expectedPaths is! List) {
     expectedPaths = [expectedPaths];
   }
   var collector = new DiagnosticCollector();
   var options = [];
   if (verbose) {
     options.add('--verbose');
   }
   if (enableExperimentalMirrors) {
     options.add('--enable-experimental-mirrors');
   }
-  var compiler = compilerFor(sourceFiles, diagnosticHandler: collector,
-                             packageRoot: Uri.parse('memory:/pkg/'),
-                             options: options);
-  return compiler.run(Uri.parse('memory:/main.dart')).then((_) {
-    Expect.equals(0, collector.errors.length, 'Errors: ${collector.errors}');
-    if (enableExperimentalMirrors) {
-      Expect.equals(0, collector.warnings.length,
-                    'Warnings: ${collector.errors}');
-    } else {
-      Expect.equals(1, collector.warnings.length,
-                    'Warnings: ${collector.errors}');
-      Expect.equals(
-          MessageKind.IMPORT_EXPERIMENTAL_MIRRORS.message(
-              {'importChain': expectedPaths.join(
-                  MessageKind.IMPORT_EXPERIMENTAL_MIRRORS_PADDING)}).toString(),
-          collector.warnings.first.message);
-    }
-  });
+  CompilationResult result = await runCompiler(
+      entryPoint: Uri.parse('memory:/main.dart'),
+      memorySourceFiles: sourceFiles,
+      diagnosticHandler: collector,
+      packageRoot: Uri.parse('memory:/pkg/'),
+      options: options);
+  Expect.equals(0, collector.errors.length, 'Errors: ${collector.errors}');
+  if (enableExperimentalMirrors) {
+    Expect.equals(0, collector.warnings.length,
+                  'Warnings: ${collector.errors}');
+  } else {
+    Expect.equals(1, collector.warnings.length,
+                  'Warnings: ${collector.errors}');
+    Expect.equals(
+        MessageKind.IMPORT_EXPERIMENTAL_MIRRORS,
+        collector.warnings.first.message.kind);
+    Expect.equals(
+        expectedPaths.join(MessageKind.IMPORT_EXPERIMENTAL_MIRRORS_PADDING),
+        collector.warnings.first.message.arguments['importChain']);
+  }
 }
 
 Future checkPaths(Map sourceData) {
   Map sourceFiles = sourceData;
   var expectedPaths = sourceData['paths'];
   var expectedVerbosePaths = sourceData['verbosePaths'];
   if (expectedVerbosePaths == null) {
     expectedVerbosePaths = expectedPaths;
   }
   return test(sourceFiles, expectedPaths: expectedPaths).then((_) {
@@ skipping 19 matching lines @@
       DUAL_INDIRECT_IMPORT3,
       DUAL_INDIRECT_PACKAGE_IMPORT1,
       DIRECT_EXPORT,
       INDIRECT_EXPORT1,
       INDIRECT_EXPORT2,
       INDIRECT_PACKAGE_EXPORT1,
       INDIRECT_PACKAGE_EXPORT2],
       (map) => checkPaths(map)
   ));
 }