Initial support for mixins in dartc.

compiler/java/com/google/dart/compiler/resolver/ClassAliasElement.java

Index: compiler/java/com/google/dart/compiler/resolver/ClassAliasElement.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/ClassAliasElement.java b/compiler/java/com/google/dart/compiler/resolver/ClassAliasElement.java
new file mode 100644
index 0000000000000000000000000000000000000000..c392fbdd787826241d76f70c01e8d65ff49fc092
--- /dev/null
+++ b/compiler/java/com/google/dart/compiler/resolver/ClassAliasElement.java
@@ -0,0 +1,11 @@
+// Copyright (c) 2013, 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.
+
+package com.google.dart.compiler.resolver;
+
+/**
+ * A class type alias.
+ */
+public interface ClassAliasElement extends ClassElement {
+}