http/tests/devtools/extensions/extensions-sidebar.js timeout flake

Now has graduated to a timeout on release, and a crash at times.

Tbr: findit@
No-try: true
No-presubmit: true
Bug: 946710
Change-Id: Iaeed92e95d7399642cb74e000024cda73d1b19b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1543373Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#645317}

third_party/blink/web_tests/TestExpectations

@@ -2854,8 +2854,8 @@ crbug.com/940050 virtual/threaded/external/wpt/animation-worklet/playback-rate.h
 # These need to be updated but appear not to be related to that change.
 crbug.com/626703 http/tests/devtools/indexeddb/database-refresh-view.js [ Pass Failure ]
 crbug.com/626703 virtual/binary-for-devtools/http/tests/devtools/indexeddb/database-refresh-view.js [ Pass Failure ]
-crbug.com/626703 http/tests/devtools/extensions/extensions-sidebar.js [ Pass Failure ]
-crbug.com/626703 virtual/binary-for-devtools/http/tests/devtools/extensions/extensions-sidebar.js [ Pass Failure ]
+crbug.com/626703 crbug.com/946710 http/tests/devtools/extensions/extensions-sidebar.js [ Crash Failure Pass Timeout ]
+crbug.com/626703 crbug.com/946710 virtual/binary-for-devtools/http/tests/devtools/extensions/extensions-sidebar.js [ Crash Failure Pass Timeout ]
 crbug.com/751952 fast/text/international/complex-text-rectangle.html [ Timeout Pass ]
 crbug.com/751952 [ Mac ] editing/selection/modify_extend/extend_by_character.html [ Failure Pass ]
 crbug.com/751952 [ Win ] editing/selection/modify_extend/extend_by_character.html [ Failure Pass ]