Web Animations: Trigger and update CSS Animations backed by the Web Animations model

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index 6b2653ef397fa013056dd306653a0a2dbf4b5405..c76c63677849a8b8116ef57ddac24f5cf85d93f2 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -1013,7 +1013,7 @@ public:
     // Return a Locale for the default locale if the argument is null or empty.
     Locale& getCachedLocale(const AtomicString& locale = nullAtom);
 
-    DocumentTimeline* timeline() { return m_timeline.get(); }
+    DocumentTimeline* timeline() const { return m_timeline.get(); }
 
     void addToTopLayer(Element*, const Element* before = 0);
     void removeFromTopLayer(Element*);