Reland "Rebaseline a virtual PiP test and unskip it"

This is a reland of 82d1bd2b

Original change's description:
> Rebaseline a virtual PiP test and unskip it
> 
> TBR=foolip
> 
> Bug: 866802
> Change-Id: I633708217593c5b132beb69eeb27f7e6caeeedc0
> Reviewed-on: https://chromium-review.googlesource.com/1150632
> Reviewed-by: Robert Ma <robertma@chromium.org>
> Commit-Queue: Robert Ma <robertma@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#578084}

Bug: 866802
Change-Id: Ib6b87fa99899ec0d974c417cb6e2362ddeabcb1b
Reviewed-on: https://chromium-review.googlesource.com/1151467
Commit-Queue: Philip Jägenstedt <foolip@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578382}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3590,9 +3590,6 @@ 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 ]
 

third_party/WebKit/LayoutTests/virtual/video-surface-layer/external/wpt/picture-in-picture/idlharness.window-expected.txt

 This is a testharness.js-based test.
-PASS idlharness
 PASS picture-in-picture interfaces.
 PASS Partial interface HTMLVideoElement: original interface defined
 PASS Partial interface Document: original interface defined