Skip a virtual/ test to unblock the WPT importer

It will be enabled again after the next import.

Bug: 866802
Change-Id: Id2f4198b7699be1bdf185758401fdb74413a1f21
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1148208Reviewed-by: Jonathon Kereliuk <kereliuk@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577478}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3475,6 +3475,9 @@ crbug.com/792437 external/wpt/css/css-multicol/multicol-rule-outset-000.xht [ Fa
 crbug.com/636055 external/wpt/css/css-multicol/multicol-span-all-margin-nested-002.xht [ Failure ]
 crbug.com/792446 external/wpt/css/css-multicol/multicol-span-float-001.xht [ Failure ]
 
+# Skip a virtual test that wpt-importer is unable to update baseline for correctly.
+crbug.com/866802 virtual/video-surface-layer/external/wpt/picture-in-picture/idlharness.window.html [ Skip ]
+
 # This test times out on debug builds, see https://crbug.com/755810
 crbug.com/626703 [ Debug ] external/wpt/html/semantics/tabular-data/processing-model-1/span-limits.html [ Skip ]