Add builder tag for Safari 6.2 slave. Update status files for Safari 6.2.

tests/corelib/corelib.status

Index: tests/corelib/corelib.status
diff --git a/tests/corelib/corelib.status b/tests/corelib/corelib.status
index 16616a77aa0303952a1ff23ea30410b5f8905250..32880579106c0ce7cd6d63cd47017da3ce33cae7 100644
--- a/tests/corelib/corelib.status
+++ b/tests/corelib/corelib.status
@@ -124,11 +124,10 @@ list_as_map_test: Pass, Slow # TODO(kasperl): Please triage.
 
 [ $compiler == dart2js && ($runtime == firefox || $runtime == safari || $runtime == chrome || $runtime == drt) ]
 
-[ $compiler == dart2js && ($runtime == safari || $runtime == safarimobilesim) ]
+[ $compiler == dart2js && (($runtime == safari && $builder_tag == mac10_7) || $runtime == safarimobilesim) ]
+list_test/01: Fail # Safari bug: Array(-2) seen as dead code.
 string_trimlr_test/none: Fail
-
-[ $compiler == dart2js && $runtime == safarimobilesim ]
-string_split_test: RuntimeError  # Appears to be bug in safarimobilesim
+string_split_test: RuntimeError # Issue 21431
 
 [ $compiler == dart2js && $runtime == ie10 ]
 string_case_test/01: Fail, OK  # Bug in IE.
@@ -212,9 +211,6 @@ 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 == ie10 ]
 num_parse_test: RuntimeError  # Issue 15316
 num_parse_test/01: RuntimeError  # Issue 15316