Adjust assertions in MethodMirror.source not to expect source for implicit constructors or signatur…

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.
 
 [ $checked && $compiler != dartanalyzer && $compiler != dart2analyzer && $runtime != dartium ]
 mirrors/regress_16321_test/01: CompileTimeError # Issue 16351
 
 [ $checked && $compiler == none && ($runtime == dartium || $runtime == drt) ]
 mirrors/regress_16321_test/01: RunTimeError # Issue 16351
 
@@ skipping 216 matching lines @@
 mirrors/generic_local_function_test: RuntimeError # Issue 14913
 mirrors/symbol_validation_test: RuntimeError # Issue 13596
 mirrors/synthetic_accessor_properties_test/none: RuntimeError # Issue 14632
 mirrors/toplevel_members_test/01: RuntimeError # Issue 14632
 
 async/timer_not_available_test: SkipByDesign # only meant to test when there is no way to implement timer (currently only in d8)
 
 [ $compiler == none ]
 mirrors/mirrors_reader_test: Slow, Pass
 
-[ $compiler == none && $checked ]
-mirrors/mirrors_reader_test: Slow, RuntimeError # Issue 16588
-
 [ $compiler == none && $runtime == dartium ]
 mirrors/mirrors_reader_test: Slow, RuntimeError # Issue 16626
 
 [ $compiler == none && ( $runtime == drt || $runtime == dartium ) ]
 async/schedule_microtask6_test: Fail # Issue 10910
 mirrors/immutable_collections_test: Pass, Slow # Dartium debug uses -O0
 mirrors/library_uri_io_test: Skip # Not intended for drt as it uses dart:io.
 mirrors/local_isolate_test: Skip # http://dartbug.com/12188
 
 [ $compiler == none && ( $runtime == drt || $runtime == dartium ) ]
@@ skipping 33 matching lines @@
 
 mirrors/redirecting_factory_test/01: StaticWarning # test issue X, The return type 'Class<T2, T1>' of the redirected constructor is not assignable to 'Class<T1, T2>'
 mirrors/redirecting_factory_test/none: StaticWarning # test issue X, The return type 'Class<T2, T1>' of the redirected constructor is not assignable to 'Class<T1, T2>
 
 mirrors/fake_function_without_call_test: StaticWarning, OK # Implements Function without defining call.
 mirrors/find_in_context_fake_function_test: StaticWarning, OK # Implements Function without defining call.
 mirrors/immutable_collections_test: StaticWarning, OK # Expect failure for any type of Iterable.
 mirrors/inference_and_no_such_method_test: StaticWarning, OK # Expect to trigger noSuchMethod.
 mirrors/repeated_private_anon_mixin_app_test: StaticWarning, OK # Intentional library name conflict.
 mirrors/removed_api_test: StaticWarning, OK # Deliberately refers to undeclared members.