Gardening: media/encrypted-media/encrypted-media-waiting-for-a-key.html flaky

BUG=353792
TEST=
TBR=zmo@chromium.org

Review URL: https://codereview.chromium.org/203493006

git-svn-id: svn://svn.chromium.org/blink/trunk@169498 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -938,3 +938,4 @@ crbug.com/353763 http/tests/security/contentSecurityPolicy/1.1/frame-ancestors/f
 crbug.com/353754 fast/scrolling/hover-during-scroll.html [ Pass Failure ]
 crbug.com/353770 [ Linux ] media/encrypted-media/encrypted-media-playback-setmediakeys-after-src.html [ Pass Failure Timeout ]
 crbug.com/353790 [ Linux Win ] virtual/threaded/animations/import.html [ Pass Timeout ]
+crbug.com/353792 media/encrypted-media/encrypted-media-waiting-for-a-key.html [ Pass Failure Crash ]