Fix animations not starting on detached elements

Source/core/testing/Internals.idl

Index: Source/core/testing/Internals.idl
diff --git a/Source/core/testing/Internals.idl b/Source/core/testing/Internals.idl
index 4da892cd28d93c8b955d307d9e56d00ac50786a4..e39e8f9146a88fa5e514d4adb0748f6be725b17d 100644
--- a/Source/core/testing/Internals.idl
+++ b/Source/core/testing/Internals.idl
@@ -68,8 +68,9 @@
     [RaisesException] Element? elementFromPoint(Document document, double x, double y, boolean ignoreClipping, boolean allowChildFrameContent);
     [RaisesException] void clearHitTestCache(Document document);
 
-    // CSS Animation and Transition testing.
+    // Animation testing.
     [RaisesException] void pauseAnimations(double pauseTime);
+    bool isCompositedAnimation(Animation animation);
 
     // Modifies m_desiredFrameStartTime in BitmapImage to advance the next frame time
     // for testing whether animated images work properly.