Flag that --dump-info is not supported for dart2dart.

pkg/compiler/lib/src/compiler.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 dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 1041 matching lines @@
     closureMapping.ClosureNamer closureNamer;
     if (emitJavaScript) {
       js_backend.JavaScriptBackend jsBackend =
           new js_backend.JavaScriptBackend(this, generateSourceMap);
       closureNamer = jsBackend.namer;
       backend = jsBackend;
     } else {
       closureNamer = new closureMapping.ClosureNamer();
       backend = new dart_backend.DartBackend(this, strips,
                                              multiFile: dart2dartMultiFile);
+      if (dumpInfo) {
+        throw new ArgumentError('--dump-info is not supported for dart2dart.');
+      }
     }
 
     tasks = [
       libraryLoader = new LibraryLoaderTask(this),
       scanner = new ScannerTask(this),
       dietParser = new DietParserTask(this),
       parser = new ParserTask(this),
       patchParser = new PatchParserTask(this),
       resolver = new ResolverTask(this, backend.constantCompilerTask),
       closureToClassMapper = new closureMapping.ClosureTask(this, closureNamer),
@@ skipping 1345 matching lines @@
     return futureClass.computeType(compiler).createInstantiation([elementType]);
   }
 
   @override
   InterfaceType streamType([DartType elementType = const DynamicType()]) {
     return streamClass.computeType(compiler).createInstantiation([elementType]);
   }
 }
 
 typedef void InternalErrorFunction(Spannable location, String message);