fast-startup: do not emit inherit calls for classes from different fragments

tests/compiler/dart2js_extra/deferred_inheritance_test.dart

+// Copyright (c) 2016, 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.
+
+/// Regression test for --fast-startup. The compiler used to emit inherit calls
+/// on each fragment even for classes that were already loaded on a different
+/// fragment. As a result, the inheritance chain was overwritten in non-chrome
+/// browsers (by using __proto__, we evaded this issue in Chrome).
+library deferred_inheritance_test;
+
+import 'deferred_inheritance_lib2.dart';
+import 'deferred_inheritance_lib1.dart' deferred as d;
+
+import 'package:expect/expect.dart';
+
+class B extends A {}
+
+/// If the check `y is A` is generated as `y.$isA` then the issue is not
+/// exposed. We use `AssumeDynamic` to ensure that we generate as `y instanceof
+/// A` in JS.
+@NoInline() @AssumeDynamic()
+check(y) => Expect.isTrue(y is A);
+
+main() {
+  check(new B());
+  d.loadLibrary().then((_) {
+      check(new d.C());
+      check(new B()); // This fails if we overwrite the inheritance chain.
+  });
+}