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

third_party/WebKit/Source/core/animation/DocumentAnimations.h

Index: third_party/WebKit/Source/core/animation/DocumentAnimations.h
diff --git a/third_party/WebKit/Source/core/animation/DocumentAnimations.h b/third_party/WebKit/Source/core/animation/DocumentAnimations.h
index f3e01b39e66955bf94a87e62d6680b70f4231576..96733c6364003ef31ea4e9a076eb96d2323b6421 100644
--- a/third_party/WebKit/Source/core/animation/DocumentAnimations.h
+++ b/third_party/WebKit/Source/core/animation/DocumentAnimations.h
@@ -33,6 +33,8 @@
 
 #include "core/CSSPropertyNames.h"
 #include "core/dom/DocumentLifecycle.h"
+#include "platform/graphics/compositing/PaintArtifactCompositor.h"
+#include "wtf/Optional.h"
 
 namespace blink {
 
@@ -48,7 +50,8 @@ class DocumentAnimations {
   // lifecycle) frame.
   static void updateAnimations(
       Document&,
-      DocumentLifecycle::LifecycleState requiredLifecycleState);
+      DocumentLifecycle::LifecycleState requiredLifecycleState,
+      Optional<CompositorElementIdSet>&);
 
  private:
   DocumentAnimations() {}