Ensure interfaces are loaded.

dart/tests/compiler/dart2js/mock_compiler.dart

Index: dart/tests/compiler/dart2js/mock_compiler.dart
diff --git a/dart/tests/compiler/dart2js/mock_compiler.dart b/dart/tests/compiler/dart2js/mock_compiler.dart
index 8694ef6b7ec80141f3c4964de7b108c03bd480fc..f26db798cde7efadce57c38e2a911f0ab1c3bc18 100644
--- a/dart/tests/compiler/dart2js/mock_compiler.dart
+++ b/dart/tests/compiler/dart2js/mock_compiler.dart
@@ -11,6 +11,7 @@
 #import('../../../lib/compiler/implementation/source_file.dart');
 #import("../../../lib/compiler/implementation/tree/tree.dart");
 #import("../../../lib/compiler/implementation/util/util.dart");
+#import('../../../lib/compiler/compiler.dart', prefix: 'api');
 #import("parser_helper.dart");
 
 class WarningMessage {
@@ -105,6 +106,15 @@ class MockCompiler extends Compiler {
     errors.add(new WarningMessage(node, message.message));
   }
 
+  void reportMessage(SourceSpan span, var message, api.Diagnostic kind) {
+    var diagnostic = new WarningMessage(null, message.message);
+    if (kind === api.Diagnostic.ERROR) {
+      errors.add(diagnostic);
+    } else {
+      warnings.add(diagnostic);
+    }
+  }
+
   void reportDiagnostic(SourceSpan span, String message, var kind) {
     print(message);
   }