Very simple version of Isolates.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index c9c44d0cd28ee546f80eb9ac036658e40b422647..2f33312a346b11003f870d5015afc5ead9297766 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -7,7 +7,6 @@ mirrors/delegate_test: RuntimeError # Issue 13864
 
 [ $compiler == dart2js ]
 async/schedule_microtask3_test: RuntimeError # _enqueueImmediate runs after Timer. http://dartbug.com/9002
-async/schedule_microtask4_test: Pass, RuntimeError # no global exception handler in isolates. http://dartbug.com/9012
 async/schedule_microtask6_test: RuntimeError # global error handling is not supported. http://dartbug.com/5958
 
 math/double_pow_test: RuntimeError
@@ -179,7 +178,6 @@ mirrors/typevariable_mirror_metadata_test/none: RuntimeError # Issue 12282
 mirrors/type_variable_owner_test: RuntimeError # Issue 14240
 mirrors/class_mirror_type_variables_test/01: RuntimeError # Issue 14240
 
-async/timer_isolate_test: Skip # See Issue 4997
 async/timer_not_available_test: SkipByDesign # only meant to test when there is no way to implement timer (currently only in d8)
 
 [ $compiler == none && ( $runtime == drt || $runtime == dartium ) ]
@@ -187,7 +185,6 @@ mirrors/immutable_collections_test: Fail # Issue 11857, Issue 14321
 mirrors/library_uri_io_test: Skip # Not intended for drt as it uses dart:io.
 mirrors/local_isolate_test: Skip # http://dartbug.com/12188
 async/schedule_microtask6_test: Fail # Issue 10910
-async/schedule_microtask4_test: Fail # Issue 13921
 
 [ $compiler == none && $runtime == drt && $system == windows ]
 async/multiple_timer_test: Fail, Pass # See Issue 10982