Fix a stack overflow when loading transformers.

test/dependency_computer/cycle_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.
 
 library pub_tests;
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
 
@@ skipping 187 matching lines @@
       }),
       d.dir('lib', [
         d.file("myapp.dart", transformer(['foo.dart'])),
         d.file("foo.dart", "import 'bar.dart';"),
         d.file("bar.dart", "import 'myapp.dart';"),
       ])
     ]).create();
 
     expectDependencies({'myapp': []});
   });
+
+  // Regression test for #1298
+  integration("allows a single-package import cycle with two uses of "
+      "the same transformer", () {
+     d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": ["myapp", "myapp"]
+      }),
+      d.dir('lib', [
+        d.file("myapp.dart", transformer(['foo.dart'])),
+        d.file("foo.dart", "import 'bar.dart';"),
+        d.file("bar.dart", "import 'myapp.dart';"),
+      ])
+    ]).create();
+
+    expectDependencies({'myapp': []});
+  });
 }