[css-variables] Forbid var-* properties from showing up as attributes on CSSStyleDeclaration.

Author: tabatkins

css-variables/Overview.html

@@ -751,6 +751,15 @@ <h3 id=the-cssstyledeclaration-interface><span class=secno>4.1. </span>
 }
 </pre>
 
+  <p> While the CSSStyleDeclaration interface normally contains attributes
+   that are camel-cased name variants of all CSS properties (and sometimes
+   also attributes for their canonical names), it must not contain any such
+   attributes for custom properties. The camel-case trick does not work, as
+   custom property names are case-sensitive, and there are potentially an
+   infinity of custom properties, which is incompatible with the normal
+   behavior of exposing every property whether it was set in the
+   corresponding declaration block or not.
+
   <h4 id=serializing-custom-props><span class=secno>4.1.1. </span>
    Serializing Custom Properties</h4>
 

css-variables/Overview.src.html

@@ -545,6 +545,15 @@ <h3 id='the-cssstyledeclaration-interface'>
 	}
 	</pre>
 
+	While the CSSStyleDeclaration interface normally contains attributes that are camel-cased name variants of all CSS properties
+	(and sometimes also attributes for their canonical names),
+	it must not contain any such attributes for custom properties.
+	The camel-case trick does not work,
+	as custom property names are case-sensitive,
+	and there are potentially an infinity of custom properties,
+	which is incompatible with the normal behavior of exposing every property
+	whether it was set in the corresponding declaration block or not.
+
 
 
 <h4 id='serializing-custom-props'>