Add flaky tests to TestExpectation

The tests under virtual/ are also flaky:
https://analysis.chromium.org/p/chromium/flake-portal/flakes/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVyVwsSBUZsYWtlIkxjaHJvbWl1bUBibGlua193ZWJfdGVzdHNAZXh0ZXJuYWwvd3B0L2Nzcy9maWx0ZXItZWZmZWN0cy9pZGxoYXJuZXNzLmFueS5odG1sDA

TBR=schenney@chromium.org

Bug: 1042453
Change-Id: Ib0cab652bb61b23012c12260974a5645b83e2c3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2024455Reviewed-by: Yi Gu <yigu@chromium.org>
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735939}

third_party/blink/web_tests/TestExpectations

@@ -376,6 +376,10 @@ crbug.com/1042453 [ Win ] external/wpt/css/filter-effects/idlharness.any.html [
 crbug.com/1042453 [ Mac ] external/wpt/css/filter-effects/idlharness.any.html [ Timeout Pass ]
 crbug.com/1042453 [ Win ] external/wpt/css/filter-effects/idlharness.any.worker.html [ Timeout Pass ]
 crbug.com/1042453 [ Mac ] external/wpt/css/filter-effects/idlharness.any.worker.html [ Timeout Pass ]
+crbug.com/1042453 [ Win ] virtual/scalefactor200/external/wpt/css/filter-effects/idlharness.any.html [ Timeout Pass ]
+crbug.com/1042453 [ Mac ] virtual/scalefactor200/external/wpt/css/filter-effects/idlharness.any.html [ Timeout Pass ]
+crbug.com/1042453 [ Win ] virtual/scalefactor200/external/wpt/css/filter-effects/idlharness.any.worker.html [ Timeout Pass ]
+crbug.com/1042453 [ Mac ] virtual/scalefactor200/external/wpt/css/filter-effects/idlharness.any.worker.html [ Timeout Pass ]
 
 crbug.com/1042783 external/wpt/css/css-backgrounds/background-size/background-size-near-zero-png.html [ Failure ]
 crbug.com/1042783 external/wpt/css/css-backgrounds/background-size/background-size-near-zero-svg.html [ Failure ]