feat: Instant CSS animations

Sets all css animations to run instantly. Creates less delay with Playwright when waiting for elements to appear.

patches/no-css-animations.patch

@@ -0,0 +1,32 @@
+diff --git a/dom/animation/AnimationEffect.cpp b/dom/animation/AnimationEffect.cpp
+index 6ef8c30d49..07cad770c9 100644
+--- a/dom/animation/AnimationEffect.cpp
++++ b/dom/animation/AnimationEffect.cpp
+@@ -108,10 +108,18 @@ ComputedTiming AnimationEffect::GetComputedTimingAt(
+   // Always return the same object to benefit from return-value optimization.
+   ComputedTiming result;
+ 
++  result.mActiveDuration = aTiming.ActiveDuration();
+   if (aTiming.Duration()) {
+     MOZ_ASSERT(aTiming.Duration().ref() >= zeroDuration,
+                "Iteration duration should be positive");
+-    result.mDuration = aTiming.Duration().ref();
++    if (result.mActiveDuration != StickyTimeDuration::Forever()) {
++      // On css animations with finite duration, set the duration & active duration to 0
++      result.mDuration = zeroDuration;
++      result.mActiveDuration = zeroDuration;
++    } else {
++      // On infinite-running animations, use the default duration
++      result.mDuration = aTiming.Duration().ref();
++    }
+   }
+ 
+   MOZ_ASSERT(aTiming.Iterations() >= 0.0 && !std::isnan(aTiming.Iterations()),
+@@ -124,7 +132,6 @@ ComputedTiming AnimationEffect::GetComputedTimingAt(
+              "ValidateIterationStart");
+   result.mIterationStart = aTiming.IterationStart();
+ 
+-  result.mActiveDuration = aTiming.ActiveDuration();
+   result.mEndTime = aTiming.EndTime();
+   result.mFill = aTiming.Fill() == dom::FillMode::Auto ? dom::FillMode::None
+                                                        : aTiming.Fill();