[SPv2] Decomposite otherwise-compositable animations that paint nothing.

third_party/WebKit/Source/core/animation/CompositorPendingAnimations.cpp

Index: third_party/WebKit/Source/core/animation/CompositorPendingAnimations.cpp
diff --git a/third_party/WebKit/Source/core/animation/CompositorPendingAnimations.cpp b/third_party/WebKit/Source/core/animation/CompositorPendingAnimations.cpp
index b99515d56dd95e8465816d595152251f87ccdf97..7fa7181a8cd6f8f1b216701913fb95cc720d67c0 100644
--- a/third_party/WebKit/Source/core/animation/CompositorPendingAnimations.cpp
+++ b/third_party/WebKit/Source/core/animation/CompositorPendingAnimations.cpp
@@ -54,7 +54,9 @@ void CompositorPendingAnimations::add(Animation* animation) {
   }
 }
 
-bool CompositorPendingAnimations::update(bool startOnCompositor) {
+bool CompositorPendingAnimations::update(
+    const Optional<CompositorElementIdSet>& compositedAnimationElementIds,
+    bool startOnCompositor) {
   HeapVector<Member<Animation>> waitingForStartTime;
   bool startedSynchronizedOnCompositor = false;
 
@@ -74,6 +76,7 @@ bool CompositorPendingAnimations::update(bool startOnCompositor) {
     // Animations with a start time do not participate in compositor start-time
     // grouping.
     if (animation->preCommit(animation->hasStartTime() ? 1 : compositorGroup,
+                             compositedAnimationElementIds,
                              startOnCompositor)) {
       if (animation->hasActiveAnimationsOnCompositor() &&
           !hadCompositorAnimation) {