Allows observers to be notified when layer animations complete.

ui/gfx/compositor/layer_animation_sequence.h

Index: ui/gfx/compositor/layer_animation_sequence.h
diff --git a/ui/gfx/compositor/layer_animation_sequence.h b/ui/gfx/compositor/layer_animation_sequence.h
index 4670587880cfd7a6e2316ced81138095f4f56524..8f377840107c4c790c51c9842b4c7e190286415b 100644
--- a/ui/gfx/compositor/layer_animation_sequence.h
+++ b/ui/gfx/compositor/layer_animation_sequence.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/memory/linked_ptr.h"
+#include "base/observer_list.h"
 #include "base/time.h"
 #include "ui/gfx/compositor/compositor_export.h"
 #include "ui/gfx/compositor/layer_animation_element.h"
@@ -16,6 +17,7 @@
 namespace ui {
 
 class LayerAnimationDelegate;
+class LayerAnimationObserver;
 
 // Contains a collection of layer animation elements to be played one after
 // another. Although it has a similar interface to LayerAnimationElement, it is
@@ -67,6 +69,14 @@ class COMPOSITOR_EXPORT LayerAnimationSequence {
   bool HasCommonProperty(
       const LayerAnimationElement::AnimatableProperties& other) const;
 
+  // These functions are used for adding or removing observers from the observer
+  // list. The observers are notified when animations end.
+  void AddObserver(LayerAnimationObserver* observer);
+  void RemoveObserver(LayerAnimationObserver* observer);
+
+  // Notifies the observers that this sequence has ended.
+  void NotifyEnded();
+
  private:
   typedef std::vector<linked_ptr<LayerAnimationElement> > Elements;
 
@@ -86,6 +96,9 @@ class COMPOSITOR_EXPORT LayerAnimationSequence {
   size_t last_element_;
   base::TimeDelta last_start_;
 
+  // These parties are notified when layer animations end.
+  ObserverList<LayerAnimationObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerAnimationSequence);
 };