[css-view-transitions-2] Make some syntax clarifications (w3c#10158)

- Add [SameObject] to CSSOM
- Clarify that classes can't include white space

Author: noamr

css-view-transitions-2/Overview.bs

@@ -449,7 +449,7 @@ The {{CSSViewTransitionRule}} represents a ''@view-transition'' rule.
 		[Exposed=Window]
 		interface CSSViewTransitionRule : CSSRule {
 			readonly attribute ViewTransitionNavigation navigation;
-			readonly attribute FrozenArray<CSSOMString> types;
+			[SameObject] readonly attribute FrozenArray<CSSOMString> types;
 		};
 </xmp>
 
@@ -675,10 +675,15 @@ div.box {
 	<<pt-name-and-class-selector>> has the following syntax definition:
 
 	<pre class=prod>
-		<dfn>&lt;pt-name-and-class-selector></dfn> = <<pt-name-selector>><<pt-class-selector>>? | <<pt-class-selector>>
+		<dfn>&lt;pt-name-and-class-selector></dfn> = <<pt-name-selector>> <<pt-class-selector>>? | <<pt-class-selector>>
 		<dfn>&lt;pt-class-selector></dfn> = ['.' <<custom-ident>>]+
 	</pre>
 
+	When interpreting the above grammar, white space is forbidden:
+
+		* Between <<pt-name-selector>> and <<pt-class-selector>>
+		* Between any of the components of <<pt-class-selector>>.
+
 	A [=named view transition pseudo-element=] [=selector=] which has one or more <<custom-ident>> values
 	in its <<pt-class-selector>> would only match an element if the [=captured element/class list=] value in
 	[=ViewTransition/named elements=] for the pseudo-element's 'view-transition-name' [=list/contains=] all of those values.