Declare onFinish event handler for AnimationPlayer

Source/core/animation/DocumentTimeline.cpp

Index: Source/core/animation/DocumentTimeline.cpp
diff --git a/Source/core/animation/DocumentTimeline.cpp b/Source/core/animation/DocumentTimeline.cpp
index 77ef592d566ff005da38639a7d62257444a653db..648445947aa0abc069b03211a3239c9289e40ff6 100644
--- a/Source/core/animation/DocumentTimeline.cpp
+++ b/Source/core/animation/DocumentTimeline.cpp
@@ -70,7 +70,7 @@ DocumentTimeline::~DocumentTimeline()
 
 AnimationPlayer* DocumentTimeline::createAnimationPlayer(TimedItem* child)
 {
-    RefPtr<AnimationPlayer> player = AnimationPlayer::create(*this, child);
+    RefPtr<AnimationPlayer> player = AnimationPlayer::create(m_document->contextDocument().get(), *this, child);
     AnimationPlayer* result = player.get();
     m_players.add(result);
     setOutdatedAnimationPlayer(result);
@@ -79,6 +79,8 @@ AnimationPlayer* DocumentTimeline::createAnimationPlayer(TimedItem* child)
 
 AnimationPlayer* DocumentTimeline::play(TimedItem* child)
 {
+    if (!m_document)
+        return 0;
     AnimationPlayer* player = createAnimationPlayer(child);
     player->setStartTime(effectiveTime());
     return player;
@@ -190,6 +192,7 @@ size_t DocumentTimeline::numberOfActiveAnimationsForTesting() const
 }
 
 void DocumentTimeline::detachFromDocument() {
+    // FIXME: DocumentTimeline should keep Document alive.
     m_document = 0;
 }