Avoid inlining constants that are used via a deferred import.

sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.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 dart_tree;
 
 import '../dart2jslib.dart' as dart2js;
 import '../dart_types.dart';
 import '../util/util.dart';
 import '../elements/elements.dart'
@@ skipping 750 matching lines @@
     return unimplemented();
   }
 
   ast.Expression visitInterceptor(dart2js.InterceptorConstant constant) {
     return unimplemented();
   }
 
   ast.Expression visitDummy(dart2js.DummyConstant constant) {
     return unimplemented();
   }
+
+  ast.Expression visitDeferred(dart2js.DeferredConstant constant) {
+    return unimplemented();
+  }
 }