Defer starting of animations until after compositing update

Source/core/rendering/compositing/RenderLayerCompositor.cpp

Index: Source/core/rendering/compositing/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.cpp b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
index b41e690d771a4e3cfa654d666a2c531d24db9dd8..1a941e9b7e3c8d58d46034ba5a7e6bac26a8f959 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -401,8 +401,18 @@ void RenderLayerCompositor::updateCompositingLayers()
         return;
 
     lifecycle().advanceTo(DocumentLifecycle::InCompositingUpdate);
-    DocumentLifecycle::Scope lifecycleScope(lifecycle(), DocumentLifecycle::CompositingClean);
 
+    updateCompositingLayersInternal();
+
+    lifecycle().advanceTo(DocumentLifecycle::CompositingClean);
+
+    DocumentAnimations::startPendingAnimations(m_renderView->document());
+    DocumentAnimations::dispatchAnimationEventsAsync(m_renderView->document());
+    ASSERT(m_renderView->document().lifecycle().state() == DocumentLifecycle::CompositingClean);
+}
+
+void RenderLayerCompositor::updateCompositingLayersInternal()
+{
     if (isMainFrame() && m_renderView->frameView())
         finishCompositingUpdateForFrameTree(&m_renderView->frameView()->frame());