[css-text-decor-4] Add from-font keyword to text-decoration-width/tex…

…t-underline-offset per WG resolution. Fixes w3c#2376

css-text-decor-4/Overview.bs

@@ -35,7 +35,7 @@ Text Decoration Line Thickness: the 'text-decoration-width' property</h3>
 
 	<pre class="propdef">
 			Name: text-decoration-width
-			Value: auto | <<length>>
+			Value: auto | from-font | <<length>>
 			Initial: auto
 			Applies to: all elements
 			Inherited: no
@@ -56,6 +56,13 @@ Text Decoration Line Thickness: the 'text-decoration-width' property</h3>
 			The UA chooses an appropriate thickness for text decoration lines;
 			see below.
 
+		<dt><dfn>from-font</dfn>
+		<dd>
+			If the <a>first available font</a> has
+			metrics indicating a preferred underline width,
+			use that width,
+			otherwise behaves as ''text-decoration-width/auto''.
+
 		<dt><dfn><<length>></dfn>
 		<dd>
 			Specifies the thickness of text decoration lines as a length.
@@ -168,7 +175,7 @@ Text Underline Offset: the 'text-underline-offset' property</h3>
 
 	<pre class="propdef">
 			Name: text-underline-offset
-			Value: auto | <<length>>
+			Value: auto | from-font | <<length>>
 			Initial: auto
 			Applies to: all elements
 			Inherited: yes
@@ -188,6 +195,13 @@ Text Underline Offset: the 'text-underline-offset' property</h3>
 		<dd>
 			The UA chooses an appropriate offset for underlines.
 
+		<dt><dfn>from-font</dfn>
+		<dd>
+			If the <a>first available font</a> has
+			metrics indicating a preferred underline offset,
+			use that offset,
+			otherwise behaves as ''text-underline-offset/auto''.
+
 		<dt><dfn><<length>>
 		<dd>
 			Specifies the offset of underlines as a length.