[view-transitions] Fix incomplete pausing of animations in reftests.

The 50s duration on pseudo-renderiong-invalidation still permitted
drift in pixel values, presumably due to cross-fade brightening.
Replaced with a pause.  The other tests were pausing on the group, but
animation-play-state is non-inheritted so animation in the image-pair,
old, and new were still running. These are all paused now.

Bug: 324915834, 343288729

Change-Id: I56b9f13e41121787faef21e19d204399f8a2bc2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6409153
Reviewed-by: Vladimir Levin <[email protected]>
Commit-Queue: Kevin Ellis <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1439621}

Author: kevers-google

css/css-view-transitions/active-view-transition-on-non-root.html

@@ -21,7 +21,10 @@
   background: red;
 }
 
-::view-transition-group(*) {
+::view-transition-group(*),
+::view-transition-image-pair(*),
+::view-transition-old(*),
+::view-transition-new(*) {
   animation-play-state: paused;
 }
 </style>

css/css-view-transitions/active-view-transition-type-on-non-root.html

@@ -21,7 +21,10 @@
   background: red;
 }
 
-::view-transition-group(*) {
+::view-transition-group(*),
+::view-transition-image-pair(*),
+::view-transition-old(*),
+::view-transition-new(*) {
   animation-play-state: paused;
 }
 </style>

css/css-view-transitions/pseudo-rendering-invalidation.html

@@ -28,8 +28,11 @@
   background: darkseagreen;
 }
 
-::view-transition-group(*) {
-  animation-duration: 50s;
+::view-transition-group(*),
+::view-transition-image-pair(*),
+::view-transition-old(*),
+::view-transition-new(*) {
+  animation-play-state: paused;
 }
 
 ::view-transition {