external/wpt/background-fetch/ tests are flaking on MSAN linux

These tests have been observed to repeatedly crash on
WebKit Linux Trusty MSAN

Bug: 869818
No-try: True
No-presubmit: True
Change-Id: Ieb9d7a9ce970960051ab480001a61f6db9bb8bf5
Reviewed-on: https://chromium-review.googlesource.com/1158464Reviewed-by: Christos Froussios <cfroussios@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579760}

third_party/WebKit/LayoutTests/MSANExpectations

@@ -163,3 +163,9 @@ crbug.com/856601 [ Linux ] virtual/outofblink-cors/external/wpt/fetch/cors-rfc19
 crbug.com/856601 [ Linux ] virtual/outofblink-cors/external/wpt/service-workers/service-worker/interfaces-sw.https.html [ Timeout Pass ]
 crbug.com/856601 [ Linux ] virtual/service-worker-servicification/external/wpt/service-workers/service-worker/interfaces-sw.https.html [ Timeout Pass ]
 crbug.com/856601 [ Linux ] virtual/video-surface-layer/external/wpt/picture-in-picture/idlharness.window.html [ Pass Timeout ]
+
+# background-fetch tests crash on MSAN
+crbug.com/869818 [ Linux ] external/wpt/background-fetch/get-ids.https.window.html [ Pass Crash ]
+crbug.com/869818 [ Linux ] external/wpt/background-fetch/get.https.window.html [ Pass Crash ]
+crbug.com/869818 [ Linux ] external/wpt/background-fetch/mixed-content-and-allowed-schemes.https.window.html [ Pass Crash ]
+crbug.com/869818 [ Linux ] external/wpt/background-fetch/port-blocking.https.window.html [ Pass Crash ]