[css-masking-1] Just reference border-image property grammars directly. #13681

Author: tabatkins

css-masking-1/Overview.bs

@@ -53,6 +53,8 @@ spec:css-backgrounds-3; type:property;
     text:border-image-repeat
     text:border-image-slice
     text:border-image-width
+    text:border-image-source
+    text:border-image-outset
     text:border-radius
     text:border-width
 spec:css-color-4; type:property
@@ -1527,7 +1529,7 @@ These pieces may be sliced, scaled and stretched in various ways to fit the size
 
 <pre class=propdef>
 Name: mask-border-source
-Value: none | <<image>>
+Value: <<'border-image-source'>>
 Initial: none
 Applies to: All elements. In SVG, it applies to <a>container elements</a> excluding the <a element>defs</a> element, all <a>graphics elements</a> and the <a element>use</a> element
 Inherited: no
@@ -1587,7 +1589,7 @@ The 'mask-mode' and 'mask-type' properties must have no affect on the <a>mask bo
 
 <pre class=propdef>
 Name: mask-border-slice
-Value: [ <<number>> | <<percentage>> ]{1,4} && fill?
+Value: <<'border-image-slice'>>
 Initial: 0
 Applies to: All elements. In SVG, it applies to <a>container elements</a> excluding the <a element>defs</a> element, all <a>graphics elements</a> and the <a element>use</a> element
 Inherited: no
@@ -1612,7 +1614,7 @@ See the 'border-image-slice' property [[!CSS3BG]] for the definitions of the pro
 
 <pre class=propdef>
 Name: mask-border-width
-Value: [ <<length-percentage>> | <<number>> | auto ]{1,4}
+Value: <<'border-image-width'>>
 Initial: auto
 Applies to: All elements. In SVG, it applies to <a>container elements</a> excluding the <a element>defs</a> element, all <a>graphics elements</a> and the <a element>use</a> element
 Inherited: no
@@ -1638,7 +1640,7 @@ Note: For SVG elements without an associated layout box the 'border-width' is co
 
 <pre class=propdef>
 Name: mask-border-outset
-Value: [ <<length>> | <<number>> ]{1,4}
+Value: <<'border-image-outset'>>
 Initial: 0
 Applies to: All elements. In SVG, it applies to <a>container elements</a> excluding the <a element>defs</a> element, all <a>graphics elements</a> and the <a element>use</a> element
 Inherited: no
@@ -1664,7 +1666,7 @@ Note: For SVG elements without associated layout box the 'border-width' is consi
 
 <pre class=propdef>
 Name: mask-border-repeat
-Value: [ stretch | repeat | round | space ]{1,2}
+Value: <<'border-image-repeat'>>
 Initial: stretch
 Applies to: All elements. In SVG, it applies to <a>container elements</a> excluding the <a element>defs</a> element, all <a>graphics elements</a> and the <a element>use</a> element
 Inherited: no