Disable test media/video-currentTime.html

media/video-currentTime.html is flaky on Mac 10.13.
https://ci.chromium.org/p/chromium/builders/ci/Mac10.13%20Tests%20%28dbg%29

TBR=srirama.m@samsung.com

Bug: 1015975
Change-Id: I437a177d43f614653c26ab4369d15d62c7021cc6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869683Reviewed-by: Lan Wei <lanwei@chromium.org>
Commit-Queue: Lan Wei <lanwei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707548}

third_party/blink/web_tests/TestExpectations

@@ -5764,3 +5764,5 @@ crbug.com/996250 external/wpt/web-nfc/NFCReader_scan_iframe.https.html [ Timeout
 crbug.com/1015254 [ Mac ] external/wpt/pointerevents/extension/pointerevent_coalesced_events_attributes.html [ Pass Failure ]
 crbug.com/1015859 [ Linux ] http/tests/devtools/a11y-axe-core/performance/landing-page-a11y-test.js [ Pass Failure ]
 crbug.com/1015764 compositing/video/video-poster.html [ Pass Crash ]
+crbug.com/1015975 media/video-currentTime.html [ Pass Failure ]
+crbug.com/1015975 virtual/audio-service/media/video-currentTime.html [ Pass Failure ]