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

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

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 36 matching lines @@
   Document* document = animation->timeline()->document();
   if (document->view())
     document->view()->scheduleAnimation();
 
   bool visible = document->page() && document->page()->isPageVisible();
   if (!visible && !m_timer.isActive()) {
     m_timer.startOneShot(0, BLINK_FROM_HERE);
   }
 }
 
-bool CompositorPendingAnimations::update(bool startOnCompositor) {
+bool CompositorPendingAnimations::update(
+    const Optional<CompositorElementIdSet>& compositedAnimationElementIds,
+    bool startOnCompositor) {
   HeapVector<Member<Animation>> waitingForStartTime;
   bool startedSynchronizedOnCompositor = false;
 
   HeapVector<Member<Animation>> animations;
   HeapVector<Member<Animation>> deferred;
   animations.swap(m_pending);
   int compositorGroup = ++m_compositorGroup;
   while (compositorGroup == 0 || compositorGroup == 1) {
     // Wrap around, skipping 0, 1.
     // * 0 is reserved for automatic assignment
     // * 1 is used for animations with a specified start time
     compositorGroup = ++m_compositorGroup;
   }
 
   for (auto& animation : animations) {
     bool hadCompositorAnimation = animation->hasActiveAnimationsOnCompositor();
     // 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) {
         startedSynchronizedOnCompositor = true;
       }
 
       if (animation->playing() && !animation->hasStartTime() &&
           animation->timeline() && animation->timeline()->isActive()) {
         waitingForStartTime.push_back(animation.get());
       }
@@ skipping 73 matching lines @@
                                          animation->timeline()->zeroTime());
   }
 }
 
 DEFINE_TRACE(CompositorPendingAnimations) {
   visitor->trace(m_pending);
   visitor->trace(m_waitingForCompositorAnimationStart);
 }
 
 }  // namespace blink