Remove the core library stubbing infrastructure.

pkg/pkg.status

 # Copyright (c) 2012, 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.
 
 # Don't run any test-like files that show up in packages directories. It
 # shouldn't be necessary to run "pub install" in these packages, but if you do
 # it shouldn't break the tests.
 */packages/*/*: Skip
 */*/packages/*/*: Skip
 */*/*/packages/*/*: Skip
@@ skipping 106 matching lines @@
 [ $browser ]
 */test/analyzer_test: SkipByDesign # No need to run analysis tests on browser bots
 analysis_server/test/*: SkipByDesign # Uses dart:io.
 analysis_server/tool/spec/check_all_test: SkipByDesign # Uses dart:io.
 analyzer/test/*: SkipByDesign # Uses dart:io.
 analyzer2dart/*: SkipByDesign # Uses dart:io.
 docgen/test/*: SkipByDesign # Uses dart:io.
 http_server/test/*: Fail, OK # Uses dart:io.
 observe/test/transformer_test: Fail, OK # Uses dart:io.
 observe/test/unique_message_test: SkipByDesign  # Uses dart:io.
-stub_core_library/test/*: Fail, OK # Uses dart:io.
 
 [ $runtime == vm && ($arch == simarm64 || $arch == simarm || $arch == simarmv5te || $arch == simmips || $arch == armv5te) ]
 # Timeout. These are not unit tests. They do not run efficiently on our
 # simulator or low-end devices.
 *: Skip
 
 [ $runtime == vm ]
 # Skip tests on the VM if the package depends on dart:html
 mutation_observer: Skip
 
@@ skipping 42 matching lines @@
 analyzer/test/src/util/asserts_test: Crash #  try/finally
 analyzer/test/src/util/lru_map_test: Crash #  try/finally
 analyzer2dart/test/driver_test: Crash # unsupported element kind: _escapeRegExp:field
 analyzer2dart/test/end2end_test: Crash # unsupported element kind: _escapeRegExp:field
 analyzer2dart/test/identifier_semantics_test: Crash # unsupported element kind: NOT_SDK:field
 analyzer2dart/test/sexpr_test: Crash # unsupported element kind: _escapeRegExp:field
 analyzer2dart/test/tree_shaker_test: Crash # unsupported element kind: _escapeRegExp:field
 fixnum/test/int_32_test: Crash #  try/finally
 fixnum/test/int_64_test: Crash #  try/finally
 js_ast/test/printer_callback_test: Crash # unsupported element kind: templateManager:field
-stub_core_library/test/stub_test: Crash #  try/finally
 typed_data/test/typed_buffers_test/01: Crash # unsupported element kind: _escapeRegExp:field
 typed_data/test/typed_buffers_test/none: Crash # unsupported element kind: _escapeRegExp:field
 typed_mock/test/typed_mock_test: Crash #  try/finally