Mark a test that has become flaky

tests/standalone/standalone.status

Index: tests/standalone/standalone.status
diff --git a/tests/standalone/standalone.status b/tests/standalone/standalone.status
index fed76aadb641800facaed00864e40d729348bb5a..f3c979961370e8cd944e52dc7113c76e99d3507d 100644
--- a/tests/standalone/standalone.status
+++ b/tests/standalone/standalone.status
@@ -8,6 +8,7 @@
 # prefix.
 
 io/raw_socket_test: Pass, RuntimeError # Issue 28288
+io/http_close_test: Pass, RuntimeError # Issue 28380
 
 packages_file_test: Skip # Issue 26715
 packages_file_test/none: Skip   # contains no tests.
@@ -21,7 +22,7 @@ package/scenarios/invalid/same_package_twice_test.dart: RuntimeError, CompileTim
 
 issue14236_test: Pass # Do not remove this line. It serves as a marker for Issue 14516 comment #4.
 
-[ ($runtime != vm && $runtime != dart_precompiled) && ($runtime != drt || $compiler != none)) ]
+[ ($runtime != vm && $runtime != dart_precompiled) && ($runtime != drt || $compiler != none) ]
 no_assert_test: Fail, OK # This is testing a vm flag.
 env_test: Skip # This is testing a vm command line parsing scenario.