Mark http/tests/devtools/console/console-context-selector.js flaky timeout

Tbr: petermarshall@chromium.org
Bug: 1046784
Change-Id: I075a6331f966f5f362a624210e70dc20600b71cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2592993Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837050}

third_party/blink/web_tests/TestExpectations

@@ -5925,3 +5925,6 @@ crbug.com/626703 [ Mac ] external/wpt/mediacapture-image/MediaStreamTrack-getCon
 
 # WPT importer Sheriff 2020-12-14
 crbug.com/1158672 [ Mac ] external/wpt/html/dom/idlharness.https.html?include=(Document|Window) [ Pass Failure ]
+
+# Sheriff 2020-12-14
+crbug.com/1046784 http/tests/devtools/console/console-context-selector.js [ Pass Timeout ]