Added an issue about the necessary extension to CSSStyleDeclaration.

Author: tabatkins

css-variables/Overview.src.html

@@ -300,6 +300,11 @@ <h3 id='cssom-cssvariable'>
 		</dd>
 	</dl>
 
+<h3 id='cssstyledeclaration-interface'>
+Additions to the <code>CSSStyleDeclaration</code> Interface</h3>
+
+<p class='issue'>The set of data properties is open-ended, so I'm not sure how best to represent this.  I'd like to both expose the current set of properties with a non-initial value and allow setting of arbitrary properties.  The most natural way seems to be to first, set up a getter behavior on the interface somehow that deals with data properties, and second, set up a <code>data</code> map that exposes the data properties that aren't set to their initial value.</p>
+
 <h2 id="conformance">
 Conformance</h2>