[css-animations] Allow strings for @Keyframes name and animation-name

Author: birtles

css-animations/Overview.bs

@@ -215,7 +215,7 @@ Keyframes</h2>
 	the animation may iterate zero or more times.
 
 	Keyframes are specified using a specialized CSS at-rule. A <dfn>@keyframes</dfn> rule consists of the
-	keyword "@keyframes", followed by an identifier giving a name for the animation (which will
+	keyword "@keyframes", followed by either an identifier or a string giving a name for the animation (which will
 	be referenced using 'animation-name'), followed by a set of style rules (delimited by curly
 	braces).
 
@@ -438,7 +438,7 @@ The 'animation-name' property</h3>
 	Canonical order: per grammar
 	</pre>
 
-	<dfn>&lt;single-animation-name></dfn> = none | <<custom-ident>>
+	<dfn>&lt;single-animation-name></dfn> = none | <<custom-ident>> | <<string>>
 
 	The values of 'animation-name' have the following meanings:
 
@@ -451,10 +451,16 @@ The 'animation-name' property</h3>
 		<dt><dfn><<custom-ident>></dfn>
 		<dd>
 			The animation will use the keyframes with the name specified by the <<custom-ident>>,
-			if they exist.If no such keyframes exist, there is no animation.
+			if they exist. If no such keyframes exist, there is no animation.
 
 			The <a href="https://www.w3.org/TR/css3-values/#common-keywords">CSS-wide keywords</a>
 			and keywords defined by this property are not valid animation names.
+		<dt><dfn><<string>></dfn>
+		<dd>
+			The animation will use the keyframes with the name specified by the
+			<<string>>, if they exist. If no such keyframes exist, there is no
+			animation.
+		</dd>
 	</dl>
 
 <h3 id="animation-duration">