Fix flakiness in animation tests

1. When updating the animation timeline, ensure that nodes that are
   animating are marked dirty, if necessary, so any style queries will
   force an layout flush.
2. Disable the problematic transition test suites, as they are in Gecko.
   These suites often fail when Servo is so overloaded that it cannot
   deliver frames fast enough to get more than two samples during the
   animation lifecycle.

Fixes #28334.
Fixes #26435.
Fixes #21486.

1 files changed, 4 insertions, 3 deletions

diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index b417f453cdf..f52fc0d777a 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -1702,10 +1702,12 @@ impl ScriptThread {
         true
     }
 
-    // Perform step 11.10 from https://html.spec.whatwg.org/multipage/#event-loops.
+    // Perform step 7.10 from https://html.spec.whatwg.org/multipage/#event-loop-processing-model.
+    // Described at: https://drafts.csswg.org/web-animations-1/#update-animations-and-send-events
     fn update_animations_and_send_events(&self) {
         for (_, document) in self.documents.borrow().iter() {
             document.update_animation_timeline();
+            document.maybe_mark_animating_nodes_as_dirty();
         }
 
         for (_, document) in self.documents.borrow().iter() {
@@ -3012,8 +3014,7 @@ impl ScriptThread {
             document.run_the_animation_frame_callbacks();
         }
         if tick_type.contains(AnimationTickType::CSS_ANIMATIONS_AND_TRANSITIONS) {
-            document.animations().mark_animating_nodes_as_dirty();
-            document.window().add_pending_reflow();
+            document.maybe_mark_animating_nodes_as_dirty();
         }
     }