Bug 1606771 - Add a reftest. r=kvark

Differential Revision: https://phabricator.services.mozilla.com/D59901

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/5ad1eff4ce669f10abba3e70b0be0e9cb378f651

wrench/reftests/border/border-image-round.yaml

@@ -0,0 +1,42 @@
+---
+root:
+  items:
+    - type: stacking-context
+      bounds: [0, 0, 500, 500]
+      items:
+        # The pattern fits exactly a whole number of times in the border.
+        - type: border
+          bounds: [ 50, 50, 192, 192 ]
+          width: 32
+          border-type: image
+          image-source: "border-image-src.png"
+          image-width: 96
+          image-height: 96
+          slice: [ 32 ]
+          outset: 0
+          repeat-vertical: round
+          repeat-horizontal: round
+        # The pattern has to be stretched to fit.
+        - type: border
+          bounds: [ 300, 50, 200, 200 ]
+          width: 32
+          border-type: image
+          image-source: "border-image-src.png"
+          image-width: 96
+          image-height: 96
+          slice: [ 32 ]
+          outset: 0
+          repeat-vertical: round
+          repeat-horizontal: round
+        # The pattern has to be shrunk to fit.
+        - type: border
+          bounds: [ 550, 50, 180, 180 ]
+          width: 32
+          border-type: image
+          image-source: "border-image-src.png"
+          image-width: 96
+          image-height: 96
+          slice: [ 32 ]
+          outset: 0
+          repeat-vertical: round
+          repeat-horizontal: round

wrench/reftests/border/reftest.list

@@ -17,6 +17,7 @@ skip_on(android,device) fuzzy(64,24) == border-groove-simple.yaml border-groove-
 skip_on(android,device) fuzzy(64,24) == border-ridge-simple.yaml border-ridge-simple-ref.yaml  # Fails on Pixel2
 platform(linux,mac) fuzzy(1,3) == degenerate-curve.yaml degenerate-curve.png
 platform(linux,mac) == border-image.yaml border-image-ref.png
+platform(linux,mac) == border-image-round.yaml border-image-round-ref.png
 == border-image-crash.yaml border-image-crash-ref.yaml
 == border-image-fill.yaml border-image-fill-ref.png
 == border-no-bogus-line.yaml border-no-bogus-line-ref.png