VM: Always return immutable collections from the mirrors.

tests/lib/lib.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.
 
 [ $csp ]
 mirrors/delegate_test: RuntimeError # Issue 13864
 
 [ $compiler == dart2js ]
 async/schedule_microtask3_test: RuntimeError # _enqueueImmediate runs after Timer. http://dartbug.com/9002
 async/schedule_microtask4_test: Pass, RuntimeError # no global exception handler in isolates. http://dartbug.com/9012
@@ skipping 156 matching lines @@
 mirrors/native_class_test: Fail, OK # This test is meant to run in a browser.
 
 [ $compiler == none  ]
 async/schedule_microtask3_test: Fail # _enqueueImmediate runs after Timer. http://dartbug.com/9001.
 mirrors/hierarchy_test: Fail # TODO(ahe): This test is slightly broken. http://dartbug.com/12464
 mirrors/mixin_application_test/01: Fail, OK # TODO(ahe): Slight broken test to ensure test coverage on dart2js.
 mirrors/intercepted_object_test: Fail, OK # TODO(ahe): Slight broken test to ensure test coverage on dart2js.
 mirrors/typedef_test/01: Fail, OK # Incorrect dart2js behavior.
 
 mirrors/generic_f_bounded_test/01: RuntimeError # Issue 14000
-mirrors/immutable_collections_test: RuntimeError # Issue 14027
 mirrors/symbol_validation_test: RuntimeError # Issue 13596
 mirrors/typevariable_mirror_metadata_test/none: RuntimeError # Issue 12282
 mirrors/type_variable_owner_test: RuntimeError # Issue 14240
 mirrors/class_mirror_type_variables_test/01: RuntimeError # Issue 14240
 
 async/timer_isolate_test: Skip # See Issue 4997
 async/timer_not_available_test: SkipByDesign # only meant to test when there is no way to implement timer (currently only in d8)
 
 [ $compiler == none && ( $runtime == drt || $runtime == dartium ) ]
 mirrors/library_uri_io_test: Skip # Not intended for drt as it uses dart:io.
@@ skipping 55 matching lines @@
 [ ($compiler != none && $runtime != none) || ($compiler == none && ($runtime != dartium && $runtime != drt)) ]
 async/schedule_microtask_test: Fail # Issue 9001, Issue 9002
 
 [ $compiler == none && $runtime == vm && $arch == arm ]
 mirrors/find_in_context_fake_function_test: Crash # Issue 14290
 async/stream_controller_async_test: RuntimeError # Issue 14290
 async/stream_state_nonzero_timer_test: RuntimeError # Issue 14290
 async/stream_state_test: RuntimeError # Issue 14290
 async/stream_subscription_cancel_test: RuntimeError # Issue 14290