Update test expectations for encrypted-media-encrypted-event-different-origin.html

The test is not really slow -- it just happens to be the first test run
by one of the workers when running the layout tests. And the first test
run takes much longer than usual. See the bug for details.

BUG=522646
TEST=test still passes locally

Review URL: https://codereview.chromium.org/1284413005

git-svn-id: svn://svn.chromium.org/blink/trunk@200918 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -45,7 +45,7 @@ crbug.com/522640 [ Debug ] fast/dom/shadow/access-document-of-detached-styleshee
 crbug.com/522641 inspector/elements/styles-4/styles-update-links.html [ Pass Timeout ]
 crbug.com/522642 svg/animations/cssanimation-inactivedocument-crash.html [ Failure Pass ]
 crbug.com/522645 [ Linux ] virtual/android/fullscreen/video-fixed-background.html [ ImageOnlyFailure Pass ]
-crbug.com/522646 http/tests/media/encrypted-media/encrypted-media-encrypted-event-different-origin.html [ Pass Timeout ]
+crbug.com/522646 http/tests/media/encrypted-media/encrypted-media-encrypted-event-different-origin.html [ Pass Slow ]
 crbug.com/522647 http/tests/notifications/close-dispatch-asynchronous.html [ Failure Pass ]
 crbug.com/522648 fast/events/touch/compositor-touch-hit-rects-iframes.html [ Crash Failure Pass ]
 crbug.com/522649 svg/custom/js-late-pattern-and-object-creation.svg [ Failure Pass ]