Web Animations CSS: Start running animations on the compositor

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index d961ae9c1ad0f3e818207d27f316fc5c22c32092..3a042a7597337d77cf9c806be09d71dc57d3ceee 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -1434,9 +1434,15 @@ void Element::detach(const AttachContext& context)
         if (!context.resolvedStyle)
             data->resetStyleState();
 
-        if (RuntimeEnabledFeatures::webAnimationsCSSEnabled() && !context.performingReattach) {
-            if (ActiveAnimations* activeAnimations = data->activeAnimations())
-                activeAnimations->cssAnimations().cancel();
+        if (RuntimeEnabledFeatures::webAnimationsCSSEnabled()) {
+            if (ActiveAnimations* activeAnimations = data->activeAnimations()) {
+                if (context.performingReattach) {
+                    // FIXME: restart compositor animations rather than pull back to the main thread
+                    activeAnimations->cancelCompositorAnimations();
+                } else {
+                    activeAnimations->cssAnimations().cancel();
+                }
+            }
         }
     }
     if (ElementShadow* shadow = this->shadow())