Revert "Access to imports in the VM's runtime mirrors. Extend test coverage of the source mirrors."

tests/lib/mirrors/library_exports_shown_test.dart

-// 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.
-
-library test.library_imports;
-
-import 'dart:mirrors';
-import 'package:expect/expect.dart';
-import 'stringify.dart';
-
-import 'library_exports_shown.dart';
-
-test(MirrorSystem mirrors) {
-  LibraryMirror shown = mirrors.findLibrary(#library_exports_shown);
-  LibraryMirror a = mirrors.findLibrary(#library_imports_a);
-  LibraryMirror b = mirrors.findLibrary(#library_imports_b);
-
-  LibraryMirror core = mirrors.findLibrary(#dart.core);
-
-  Expect.setEquals([a, b, core],
-                   shown.libraryDependencies.map((dep) => dep.targetLibrary));
-
-  Expect.stringEquals(
-      'import dart.core\n'
-      'export library_imports_a\n'
-      ' show somethingFromA\n'
-      ' show somethingFromBoth\n'
-      'export library_imports_b\n'
-      ' show somethingFromB\n',
-      stringifyDependencies(shown));
-}
-
-main() {
-  test(currentMirrorSystem());
-}