Triage failing image-set() test

Bug: 630597
Change-Id: Ie35038b6e1546f29dc015e3ba2c5bdad73157255
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2628293Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843528}

third_party/blink/web_tests/TestExpectations

@@ -1893,7 +1893,10 @@ crbug.com/626703 external/wpt/css/css-writing-modes/sizing-orthog-vlr-in-htb-020
 crbug.com/626703 external/wpt/css/css-writing-modes/sizing-orthog-vrl-in-htb-008.xht [ Failure ]
 crbug.com/626703 external/wpt/css/css-writing-modes/sizing-orthog-vrl-in-htb-020.xht [ Failure ]
 
+# Unprefixed image-set() not supported
 crbug.com/630597 external/wpt/css/css-images/image-set/image-set-rendering.html [ Failure ]
+crbug.com/630597 external/wpt/css/css-images/image-set/image-set-content-rendering.html [ Failure ]
+
 crbug.com/604875 external/wpt/css/css-images/tiled-gradients.html [ Failure ]
 
 crbug.com/808834 [ Linux ] external/wpt/css/css-pseudo/first-letter-001.html [ Failure ]
@@ -2476,7 +2479,6 @@ crbug.com/958381 [ Mac ] external/wpt/css/CSS2/tables/table-anonymous-objects-20
 crbug.com/958381 [ Mac ] external/wpt/css/CSS2/tables/table-anonymous-objects-206.xht [ Failure ]
 
 # ====== New tests from wpt-importer added here ======
-crbug.com/626703 external/wpt/css/css-images/image-set/image-set-content-rendering.html [ Failure ]
 crbug.com/626703 external/wpt/css/css-scroll-snap/snap-after-initial-layout/scroll-snap-initial-layout-000.html [ Failure ]
 crbug.com/626703 virtual/threaded/external/wpt/css/css-scroll-snap/snap-after-initial-layout/scroll-snap-initial-layout-000.html [ Failure ]
 crbug.com/626703 [ Mac10.13 ] external/wpt/x-frame-options/multiple.html [ Timeout ]