Hack around dart:io being loaded into non-service isolates in Dartium.

tests/lib/mirrors/io_html_mutual_exclusion_test.dart

Index: tests/lib/mirrors/io_html_mutual_exclusion_test.dart
diff --git a/tests/lib/mirrors/io_html_mutual_exclusion_test.dart b/tests/lib/mirrors/io_html_mutual_exclusion_test.dart
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index 0000000000000000000000000000000000000000..087b8a63c95889f84f9b28870a972fc431aeb5af
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+++ b/tests/lib/mirrors/io_html_mutual_exclusion_test.dart
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+// Copyright (c) 2015, 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 test.io_html_mutual_exclusion;
+
+import 'dart:mirrors';
+
+main() {
+  var libraries = currentMirrorSystem().libraries;
+  bool has_io = libraries[Uri.parse('dart:io')] != null;
+  bool has_html = libraries[Uri.parse('dart:html')] != null;
+
+  if (has_io && has_html) {
+    throw "No embedder should have both dart:io and dart:html accessible";
+  }
+}