Reinstall previous behavior for Set and Queue toString.

tests/corelib/corelib.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.
 
 [ $compiler == dart2dart]
 bool_from_environment2_test: Skip
 bool_from_environment_default_value_test: Skip
 bool_from_environment_test: Skip
 int_from_environment2_test: Skip
 int_from_environment3_test: Skip
@@ skipping 38 matching lines @@
 symbol_test/01: Fail, Pass # bug 11669
 
 [ $compiler == none && $runtime != dartium && $runtime != drt && $runtime != ContentShellOnAndroid ]
 symbol_test/02: MissingCompileTimeError # bug 11669
 symbol_test/03: MissingCompileTimeError # bug 11669
 
 [ $compiler == none || $compiler == dart2dart ]
 symbol_test/none: Fail # bug 11669
 symbol_operator_test/03: Fail # bug 11669
 string_case_test/01: Fail # Bug 18061
-collection_to_string_test/none: Pass,Fail # bug 13647 (test is random, and might not encounter the error on every run)
-collection_to_string_test/01: Pass # Should be Pass,Fail,OK when the test above stops failing.
 
 [ $compiler == none && ($runtime == drt || $runtime == dartium || $runtime == ContentShellOnAndroid) ]
 main_test: Fail  # Dartium needs to check for both main() and main(args).
 
 [ $runtime == ff || $runtime == ie9 || $runtime == jsshell ]
 unicode_test: Fail
 
 [ $runtime == ff || $runtime == ie9 || $runtime == jsshell || $runtime == safari || $runtime == safarimobilesim ]
 double_round3_test: Fail, OK # Runtime rounds 0.49999999999999994 to 1.
 double_round_to_double2_test: Fail, OK # Runtime rounds 0.49999999999999994 to 1.
 
 [ $runtime == ie9 ]
 double_round4_test: Fail, OK # IE bug: Math.round(4503599627370497) != 4503599627370497.
 double_round_to_double3_test: Fail, OK # IE bug: Math.round(4503599627370497) != 4503599627370497.
 collection_length_test: Skip # Issue 12844
 
 [ $runtime == opera ]
 core_runtime_types_test: Fail
 null_nosuchmethod_test: Fail # Issue: 7413
 unicode_test: Fail # Issue 14694
 
 [ $compiler == dart2js ]
 error_stack_trace1_test: RuntimeError # Issue 12399
 hash_set_test/01: RuntimeError # Issue 11551
 integer_to_string_test/01: RuntimeError # Issue 1533
-collection_to_string_test/none: Pass, Fail # Issue 13648 (test is random, and might not encounter the error on every run)
-collection_to_string_test/01: Pass # Should be Pass,Fail,OK when the test above stops failing.
 
 big_integer_vm_test: RuntimeError, OK # VM specific test.
 bit_twiddling_bigint_test: RuntimeError # Requires bigint support.
 compare_to2_test: RuntimeError, OK    # Requires bigint support.
 string_base_vm_test: RuntimeError, OK # VM specific test.
 nan_infinity_test/01: Fail # Issue 11551
 
 [ $compiler == dart2js || $compiler == dart2dart]
 symbol_operator_test/01: CompileTimeError # Issue 15653.
 symbol_operator_test/02: CompileTimeError # Issue 15653.
@@ skipping 62 matching lines @@
 iterable_element_at_test: StaticWarning, OK # Test generates errors on purpose.
 num_clamp_test: StaticWarning, OK # Test generates errors on purpose.
 string_test: StaticWarning, OK # Test generates error on purpose.
 
 [ $compiler == dart2js && ($runtime == safari || $runtime == safarimobilesim) ]
 list_test/01: Fail # Safari bug: Array(-2) seen as dead code.
 
 [ $runtime == ie9 || $runtime == ie10 ]
 num_parse_test: RuntimeError  # Issue 15316
 num_parse_test/01: RuntimeError  # Issue 15316