[css-view-transitions-2] Resolve outbound transition promises after document unloads (#9954)

* [css-view-transitions-2] Resolve outbound transition promises after document unloads

See [this resolution](#9888 (comment))

Closes #9888

* remove bespoke task

Author: noamr

css-view-transitions-2/Overview.bs

@@ -20,7 +20,6 @@ Markup Shorthands: css yes, markdown yes
 spec:css-view-transitions-1;
 	text: active view transition; type: dfn;
 	text: capture the old state; type: dfn;
-	text: clear view transition; type: dfn;
 	text: activate view transition; type: dfn;
 	text: skip the view transition; type: dfn;
 	text: ViewTransition; type: interface;
@@ -582,11 +581,6 @@ Prepend this to the [=Perform pending transition operations=] algorithm given a
 			[=view transition params/named elements=] is a [=map/clone=] of |transition|'s [=ViewTransition/named elements=],
 			and whose [=view transition params/initial snapshot containing block size=] is |transition|'s [=ViewTransition/initial snapshot containing block size=].
 
-		1. [=Clear view transition=] |transition|.
-
-			Note: The ViewTransition object on the old Document should be destroyed after its state has been copied to the new Document below.
-				We explicitly clear it here since the old Document may be cached by the UA.
-
 		1. Call |transition|'s [=outbound post-capture steps=] given |viewTransitionParams|.
 
 
@@ -678,6 +672,8 @@ Prepend this to the [=Perform pending transition operations=] algorithm given a
 		1. Let |outboundTransition| be a new {{ViewTransition}} object in |oldDocument|'s [=relevant Realm=],
 			whose [=ViewTransition/active types=] is |resolvedRule|.
 
+			Note: the {{ViewTransition}} is skipped once the old document is hidden.
+
 		1. Set |outboundTransition|'s [=outbound post-capture steps=] to the following steps given a [=view transition params=]-or-null |params|:
 			1. Set |newDocument|'s [=inbound view transition params=] to |params|.