Re-enable AccessibilityObjectModel tests by setting the status to "test".

third_party/WebKit/LayoutTests/TestExpectations

 # Intentional failures to test the layout test system.
 Bug(intentional) harness-tests/crash.html [ Crash ]
 Bug(intentional) harness-tests/timeout.html [ Timeout ]
 
 # TODO(qyearsley): Remove these lines and uncomment other test expectation
 # lines related to CSS tests (crbug.com/706118).
 crbug.com/706118 external/wpt/css/css-flexbox-1 [ Skip ]
 crbug.com/706118 external/wpt/css/css-scoping-1 [ Skip ]
 crbug.com/706118 external/wpt/css/css-shapes-1 [ Skip ]
 crbug.com/706118 external/wpt/css/css-text-3 [ Skip ]
@@ skipping 2655 matching lines @@
 # XMLHttpRequest tests with non-deterministic results.
 crbug.com/711493 external/wpt/XMLHttpRequest/responsexml-document-properties.htm [ Failure ]
 crbug.com/711493 external/wpt/XMLHttpRequest/send-authentication-prompt-2-manual.htm [ Failure ]
 
 # Sheriff failures 2017-02-03
 crbug.com/688515 fast/spatial-navigation/snav-div-overflow-scrol-hidden.html [ Pass Failure ]
 
 # Flaky on trybots
 crbug.com/688486 external/wpt/service-workers/service-worker/fetch-request-resources.https.html [ Failure Pass ]
 
-# Flaky when run in parallel
-crbug.com/712332 accessibility/aom.html [ Failure Pass ]
-crbug.com/712332 accessibility/aom-string-properties.html [ Failure Pass ]
-
 # Sheriff failures 2017-02-21
 crbug.com/73609 http/tests/media/video-play-stall.html [ Pass Timeout ]
 crbug.com/73609 virtual/mojo-loading/http/tests/media/video-play-stall.html [ Pass Timeout ]
 
 # Sheriff failures 2017-02-27
 crbug.com/696407 [ Linux ] external/wpt/html/browsers/history/the-location-interface/location-protocol-setter-with-colon.sub.html [ Failure Pass ]
 crbug.com/694338 [ Mac10.9 ] fast/forms/calendar-picker/calendar-picker-appearance-zoom125.html [ Failure ]
 crbug.com/694338 [ Mac10.9 ] fast/forms/calendar-picker/calendar-picker-appearance-zoom200.html [ Failure ]
 
 crbug.com/697342 http/tests/push_messaging/permission-state-granted-in-document.html [ Pass Failure ]
@@ skipping 24 matching lines @@
 
 # Sheriff failures 2017-04-03
 # Should be [ Crash Pass ], but this has a commented out [ Skip ] expectation
 # for Mac earlier in the file, so just skip it everywhere.
 crbug.com/707689 shapedetection/detection-HTMLCanvasElement.html [ Skip ]
 
 # Tests to be run only under virtual/experimental-canvas-features/
 crbug.com/682753 fast/canvas-experimental [ Skip ]
 
 crbug.com/712264 external/wpt/service-workers/service-worker/fetch-event.https.html [ Failure Pass ]