Don't hide interceptors in mirrors.

sdk/lib/_internal/compiler/implementation/ssa/codegen.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.
 
 part of ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 2646 matching lines @@
   }
 
   void visitInterfaceType(HInterfaceType node) {
     List<js.Expression> typeArguments = <js.Expression>[];
     for (HInstruction type in node.inputs) {
       use(type);
       typeArguments.add(pop());
     }
 
     ClassElement cls = node.dartType.element;
-    var arguments = [
-        backend.namer.elementAccess(backend.getImplementationClass(cls))];
+    var arguments = [backend.namer.elementAccess(cls)];
     if (!typeArguments.isEmpty) {
       arguments.add(new js.ArrayInitializer.from(typeArguments));
     }
     push(js.js('#(#)', [accessHelper('buildInterfaceType'), arguments]));
   }
 
   void visitVoidType(HVoidType node) {
     push(js.js('#()', accessHelper('getVoidRuntimeType')));
   }
 
   void visitDynamicType(HDynamicType node) {
     push(js.js('#()', accessHelper('getDynamicRuntimeType')));
   }
 
   js.PropertyAccess accessHelper(String name) {
     Element helper = compiler.findHelper(name);
     if (helper == null) {
       // For mocked-up tests.
       return js.js('(void 0).$name');
     }
     world.registerStaticUse(helper);
     return backend.namer.elementAccess(helper);
   }
 }