Re-enable printing and timers in Dartium isolates (again)

tests/html/html.status

Index: tests/html/html.status
diff --git a/tests/html/html.status b/tests/html/html.status
index 19f90ff4069911be0639592c5f5c7f8f1b8c3e25..ad8a5a8259a87675700eb7a511b3636a3d0a1542 100644
--- a/tests/html/html.status
+++ b/tests/html/html.status
@@ -41,9 +41,8 @@ canvasrenderingcontext2d_test/drawImage_video_element_dataUrl: Pass,Fail # Issue
 [ $compiler == none && ($runtime == drt || $runtime == dartium || $runtime == ContentShellOnAndroid) ]
 # postMessage in dartium always transfers the typed array buffer, never a view
 postmessage_structured_test/typed_arrays: Fail
-# Dartium seems to lose the data from the dispatchEvent. 
+# Dartium seems to lose the data from the dispatchEvent.
 postmessage_structured_test/more_primitives: Fail
-async_test: Fail # Background timers not implemented.
 keyboard_event_test: Fail # Issue 13902
 isolates_test: Fail # Issue 13921
 indexeddb_3_test: Skip # Issue 19578.  Timeouts and RuntimeError
@@ -380,7 +379,6 @@ touchevent_test/supported: Fail
 xhr_test/xhr: Skip # Times out.  Issue 21527
 
 [ $compiler == none && $runtime == dartium ]
-async_test: Timeout # Issue 13719: Please triage this failure.
 element_offset_test/offset: Pass, Fail # Issue 13719, 13296
 
 [ $compiler == dartanalyzer || $compiler == dart2analyzer ]