Restrict transform animation checks to only those in-play

Currently UpdateBoxSizeAndCheckTransformAxisAlignment loops over all
animations in ElementAnimations, including otherwise-unreachable ones
which have not been garbage collected yet, which can cause the function
to loop over and test/update many completed animations unnecessarily,
hurting performance. Add a fast check to exclude animations no longer
current or in effect.

Bug: 1142176, 1142666
Change-Id: I3f489fa022df173d9dc20b198c0894dabb7bfdc1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2500604Reviewed-by: Kevin Ellis <kevers@chromium.org>
Commit-Queue: George Steel <gtsteel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821218}

third_party/blink/renderer/core/animation/element_animations.cc

@@ -142,6 +142,8 @@ bool ElementAnimations::UpdateBoxSizeAndCheckTransformAxisAlignment(
   for (auto& entry : animations_) {
     Animation& animation = *entry.key;
     if (auto* effect = DynamicTo<KeyframeEffect>(animation.effect())) {
+      if (!effect->IsCurrent() && !effect->IsInEffect())
+        continue;
       if (!effect->UpdateBoxSizeAndCheckTransformAxisAlignment(box_size))
         preserves_axis_alignment = false;
     }