Disable http/tests/devtools/tracing/worker-events.js on Mac

http/tests/devtools/tracing/worker-events.js
virtual/threaded/http/tests/devtools/tracing/worker-events.js
are flaky on Mac10.13 Tests (dbg)

Bug: 934768
No-try: True
No-presubmit: True
Change-Id: Id114e2e590e1d4642160b228cee9987b65a28c2c
Reviewed-on: https://chromium-review.googlesource.com/c/1482731Reviewed-by: Christos Froussios <cfroussios@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634607}

third_party/blink/web_tests/TestExpectations

@@ -6007,3 +6007,5 @@ crbug.com/934636 http/tests/security/cross-origin-indexeddb-allowed.html [ Crash
 crbug.com/934636 virtual/feature-policy-for-sandbox/http/tests/security/cross-origin-indexeddb-allowed.html [ Crash Pass ]
 crbug.com/934636 virtual/outofblink-cors/http/tests/security/cross-origin-indexeddb-allowed.html [ Crash Pass ]
 crbug.com/934636 virtual/outofblink-cors-ns/http/tests/security/cross-origin-indexeddb-allowed.html [ Crash Pass ]
+crbug.com/934768 [ Mac ] http/tests/devtools/tracing/worker-events.js [ Failure Pass ]
+crbug.com/934768 [ Mac ] virtual/threaded/http/tests/devtools/tracing/worker-events.js [ Failure Pass ]