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

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index bd636e43a98c5c2f623e183ea38a58fa566a4e1a..c26087dc10523cce49a3b4959a4d68b82c995ee3 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -1059,6 +1059,9 @@ abstract class Compiler implements DiagnosticListener {
       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 = [