Clarify checking for active animations

See discussion at w3c#7785

Author: khushalsagar

css-view-transitions-1/Overview.bs

@@ -893,15 +893,21 @@ The {{ViewTransition/domUpdated}} [=getter steps=] are to return [=this's=] [=Vi
     To <dfn>update transition DOM</dfn> given a {{ViewTransition}} |transition|:
 
     1. Let |document| be |transition|'s [=relevant global object's=] [=associated document=].
-
-    1. For each [=page-transition pseudo-elements=] associated with |transition|,
-        check whether there is an active animation associated with this pseudo-element.
-
-        Issue: Define what active animation means here.
-
-    1. If no [=page-transition pseudo-elements=] has an active animation:
-
-        Issue: There needs to be a definition/link for "active animation".
+	
+	1. Let |hasActiveAnimations| be a boolean, initially false. For each [=page-transition pseudo-elements=]
+        associated with |transition|:
+    
+        1. Let |element| be the [=page-transition pseudo-element=].
+    
+        1. For each |animation| with [=effect target=] set to |element| and [=animation timeline=]
+            of type [=document timeline=], set |hasActiveAnimations| to true if any of the following
+            conditions is true:
+            
+            1. |animation| is in <a lt="paused play state">paused</a> or <a lt="running play state">running</a> state.
+    
+            1. [=pending-animation-event-queue=] has any events associated with |animation|.
+
+    1. If |hasActiveAnimations| is false:
 
         1. Set |transition|'s [=ViewTransition/phase=] to "`done`".
 
@@ -1022,13 +1028,6 @@ The {{ViewTransition/domUpdated}} [=getter steps=] are to return [=this's=] [=Vi
 
 
     1. Set |transition|'s [=ViewTransition/phase=] to "`animating`".
-
-    Issue: How are keyframes scoped to user-agent origin? We could decide
-        scope based on whether `animation-name` in the computed style
-        came from a developer or UA stylesheet.
-
-    Issue: We should retarget the animation if computed properties for
-        incoming elements change.
 </div>
 
 ## [=Create transition pseudo-elements=] ## {#create-transition-pseudo-elements-algorithm}