Revert "Build Observatory with runtime"

runtime/observatory/tests/ui/retainingPath.dart

Index: runtime/observatory/tests/ui/retainingPath.dart
diff --git a/runtime/observatory/tests/ui/retainingPath.dart b/runtime/observatory/tests/ui/retainingPath.dart
deleted file mode 100644
index 119998daaa6d7522eb48fe80705c5790907ce5e2..0000000000000000000000000000000000000000
--- a/runtime/observatory/tests/ui/retainingPath.dart
+++ /dev/null
@@ -1,17 +0,0 @@
-// 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.
-
-// See reatiningPath.txt for expected behavior.
-
-class Foo {
-  var a;
-  var b;
-  Foo(this.a, this.b);
-}
-
-main() {
-  var list = new List<Foo>(10);
-  list[5] = new Foo(42.toString(), new Foo(87.toString(), 17.toString()));
-  while (true) {}
-}