Add some support for the code-point code-unit distinction.

tests/corelib/corelib.status

Index: tests/corelib/corelib.status
diff --git a/tests/corelib/corelib.status b/tests/corelib/corelib.status
index 356cedf6df48826ce4994159bec46303ec8e9d2c..4ab244b98e41e6163a9e1719e95adacd9ae5cf66 100644
--- a/tests/corelib/corelib.status
+++ b/tests/corelib/corelib.status
@@ -2,8 +2,10 @@
 # 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.
 
+reg_exp_unicode_2_test: Fail # Bug 6592
+
 [ $compiler == none ]
-unicode_test: Fail        # Bug 5163868
+unicode_test: Fail        # Bug 6706
 *dartc_test: Skip
 compare_to2_test: Fail    # Bug 4018
 null_test: Fail           # Bug 5511
@@ -14,6 +16,9 @@ apply2_test: Fail # Bug 5670
 [ $runtime == ff || $runtime == ie9 || $runtime == jsshell ]
 unicode_test: Fail
 
+[ $compiler == dart2js && ($runtime == chrome || $runtime == drt || $runtime == d8 || $runtime == safari) ]
+string_trim_unicode_test: Fail  # V8 bug 2408
+
 [ $runtime == opera ]
 core_runtime_types_test: Fail
 date_time7_test: Fail
@@ -34,6 +39,7 @@ unicode_test: Fail
 [ $compiler == dart2js ]
 math_parse_double_test: Fail # Expect.equals(expected: <78187493520>, actual: <0>)
 math_test: Fail # issue 3333
+surrogate_pair_toUpper_test: Fail # Issue 6707
 
 # Bad test, assumes RegExp.allMatches returns a Collection.
 reg_exp_all_matches_test: Fail, OK # NoSuchMethodError : method not found: 'forEach'