Ignore deferred loading from dart backend.

sdk/lib/_internal/compiler/implementation/deferred_load.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 deferred_load;
 
 import 'dart2jslib.dart' show
     Backend,
     Compiler,
     CompilerTask,
@@ skipping 745 matching lines @@
           }
         }
       });
     }
     Backend backend = compiler.backend;
     if (splitProgram && backend is JavaScriptBackend) {
       backend.registerCheckDeferredIsLoaded(compiler.globalDependencies);
     }
     if (splitProgram && backend is DartBackend) {
       // TODO(sigurdm): Implement deferred loading for dart2dart.
-      compiler.reportFatalError(
+      compiler.reportWarning(
           lastDeferred,
           MessageKind.DEFERRED_LIBRARY_DART_2_DART);
+      splitProgram = false;
     }
   }
 
   /// If [send] is a static send with a deferred element, returns the
   /// [PrefixElement] that the first prefix of the send resolves to.
   /// Otherwise returns null.
   ///
   /// Precondition: send must be static.
   ///
   /// Example:
@@ skipping 39 matching lines @@
     Element maybePrefix = elements[identifier];
     if (maybePrefix != null && maybePrefix.isPrefix) {
       PrefixElement prefixElement = maybePrefix;
       if (prefixElement.isDeferred) {
         return prefixElement;
       }
     }
     return null;
   }
 }