Add mixin support to source mirrors.

sdk/lib/_internal/compiler/implementation/elements/elements.dart

 // Copyright (c) 2012, 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 elements;
 
 
 import '../tree/tree.dart';
 import '../util/util.dart';
 import '../resolution/resolution.dart';
@@ skipping 913 matching lines @@
   /// Similar to [forEachInstanceField] but visits static fields.
   void forEachStaticField(void f(ClassElement enclosingClass, Element field));
 
   void forEachBackendMember(void f(Element member));
 
   Link<DartType> computeTypeParameters(Compiler compiler);
 }
 
 abstract class MixinApplicationElement extends ClassElement {
   ClassElement get mixin;
-  void set mixin(ClassElement value);
+  InterfaceType get mixinType;
+  void set mixinType(InterfaceType value);
   void addConstructor(FunctionElement constructor);
 }
 
 abstract class LabelElement extends Element {
   Label get label;
   String get labelName;
   TargetElement get target;
 
   bool get isTarget;
   bool get isBreakTarget;
@@ skipping 35 matching lines @@
   int get resolutionState;
   Token get beginToken;
   Token get endToken;
 
   // TODO(kasperl): Try to get rid of these.
   void set annotatedElement(Element value);
   void set resolutionState(int value);
 
   MetadataAnnotation ensureResolved(Compiler compiler);
 }