lib/convert: removed unused import, removed redundant test

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 189 matching lines @@
 [ $compiler == dart2js && $minified ]
 mirrors/intercepted_superclass_test: RuntimeError # Issue 16804
 mirrors/null_test/00: RuntimeError # Issue 16804. Please remove the multi-test comments when this test starts succeeding.
 
 [ $compiler == dart2dart ]
 mirrors/*: Skip # http://dartbug.com/11511
 async/schedule_microtask6_test: Fail             # Issue 10957 - may be related to issue 10910
 
 [ $compiler == dart2dart && $minified ]
 convert/json_lib_test: Fail # Issue 10961
-convert/json2_test:    Fail # Issue 10961
 
 [ $compiler == dart2js && $minified ]
 mirrors/typedef_test/01: Fail # http://dartbug.com/6490
 mirrors/list_constructor_test/none: Fail # http://dartbug.com/15555
 mirrors/mirrors_used_get_name_test: RuntimeError
 mirrors/mirrors_used_get_name2_test: RuntimeError
 
 [ $runtime == ff ]
 # FF setTimeout can fire early: https://bugzilla.mozilla.org/show_bug.cgi?id=291386
 convert/streamed_conversion_utf8_decode_test: Pass, Slow  # Issue 12029
@@ skipping 103 matching lines @@
 
 mirrors/deferred_mirrors_metadata_test: Fail # Issue 17522
 mirrors/metadata_scope_test/01: MissingCompileTimeError # Issue 17894
 
 [ $compiler == dart2js && $runtime == d8 && $system == windows ]
 async/*deferred*: Skip # Issue 17458
 mirrors/*deferred*: Skip # Issue 17458
 
 [ $compiler == dart2js && $mode == debug ]
 mirrors/native_class_test: Pass, Slow