Mark mojo/union.html layout test as timing out.

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 ]
 
 # ====== Oilpan-only failures from here ======
 # Most of these actually cause the tests to report success, rather than
 # failure. Expected outputs will be adjusted for the better once Oilpan
 # has been well and truly enabled always.
 
 crbug.com/569901 crbug.com/24182 [ Debug ] jquery/manipulation.html [ Timeout Pass ]
@@ skipping 2496 matching lines @@
 crbug.com/664839 http/tests/security/link-crossorigin-preload-no-cors.html [ Pass Failure ]
 crbug.com/671475 http/tests/security/suborigins/suborigin-invalid-options.html [ Pass Failure ]
 crbug.com/663876 virtual/mojo-loading/http/tests/loading/doc-write-sync-third-party-script-block-effectively-2g.html [ Pass Failure ]
 crbug.com/664816 virtual/mojo-loading/http/tests/security/contentSecurityPolicy/require-sri-for/require-sri-for-script-reportonly-blocked.php [ Pass Failure ]
 crbug.com/664819 virtual/mojo-loading/http/tests/security/isolatedWorld/bypass-main-world-csp-for-inline-style.html [ Pass Failure ]
 crbug.com/664819 virtual/mojo-loading/http/tests/security/isolatedWorld/bypass-main-world-csp-for-xhr.html [ Pass Failure ]
 crbug.com/664819 virtual/mojo-loading/http/tests/security/isolatedWorld/bypass-main-world-csp-iframes.html [ Pass Failure ]
 crbug.com/664819 virtual/mojo-loading/http/tests/security/isolatedWorld/events.html [ Pass Failure ]
 crbug.com/664839 virtual/mojo-loading/http/tests/security/link-crossorigin-preload-no-cors.html [ Pass Failure ]
 
+crbug.com/703813 mojo/union.html [ Pass Timeout ]
+
 # Possible duplicate of crbug.com/498539
 # crbug.com/664843 inspector/elements/styles-4/styles-update-from-js.html [ Pass Failure ]
 
 crbug.com/664844 media/track/track-cue-rendering-tree-is-removed-properly.html [ Pass Failure ]
 crbug.com/664844 media/track/track-default-attribute.html [ Pass Failure ]
 crbug.com/664844 media/track/track-kind-user-preference.html [ Pass Failure ]
 
 crbug.com/702837 fast/text/aat-morx.html [ Skip ]
 
 crbug.com/688670 media/track/track-cue-rendering-after-controls-removed.html [ Pass Failure ]
@@ skipping 105 matching lines @@
 crbug.com/700374 [ Win ] virtual/mojo-loading/http/tests/inspector/workers-on-navigation.html [ Failure Pass ]
 crbug.com/700374 [ Win ] http/tests/inspector/workers-on-navigation.html [ Failure Pass ]
 crbug.com/700387 [ Win7 ] external/wpt/fullscreen/api/document-exit-fullscreen-nested-in-iframe-manual.html [ Timeout Pass ]
 
 # Sheriff failures 2017-03-13
 crbug.com/701140 inspector-protocol/css/css-get-rule-list.html [ Failure Pass ]
 
 # Sheriff failures 2017-03-16
 crbug.com/701718 [ Win7 ] fast/table/border-collapsing/001-vertical.html [ Failure Pass ]
 crbug.com/701718 [ Win7 ] fast/table/border-collapsing/001.html [ Failure Pass ]