[css-view-transitions-1] Flush the callback queue before performing other view-transition operations

This ensures that a DOM update callback that skips the active
transition would take effect.

Closes w3c#11943

Author: noamr

css-view-transitions-1/Overview.bs

@@ -1235,6 +1235,10 @@ urlPrefix: https://wicg.github.io/navigation-api/; type: interface;
 
 		To <dfn>perform pending transition operations</dfn> given a {{Document}} |document|, perform the following steps:
 
+		1. [=Flush the update callback queue=].
+
+			Note: this ensures that any changes to the DOM scheduled by other skipped transitions are done before the old state for this transition is captured.
+
 		1. If |document|'s [=document/active view transition=] is not null, then:
 
 			1. If |document|'s [=document/active view transition=]'s [=ViewTransition/phase=] is "`pending-capture`",
@@ -1256,10 +1260,6 @@ urlPrefix: https://wicg.github.io/navigation-api/; type: interface;
 
 		1. Let |document| be |transition|'s [=relevant global object's=] [=associated document=].
 
-		1. [=Flush the update callback queue=].
-
-			Note: this ensures that any changes to the DOM scheduled by other skipped transitions are done before the old state for this transition is captured.
-
 		1. [=Capture the old state=] for |transition|.
 
 			If failure is returned, then [=skip the view transition=] for |transition| with an "{{InvalidStateError}}" {{DOMException}} in |transition|'s [=relevant Realm=],