Animated Rotation

ui/gfx/compositor/compositor.h

Index: ui/gfx/compositor/compositor.h
diff --git a/ui/gfx/compositor/compositor.h b/ui/gfx/compositor/compositor.h
index 42bb770cd756f0958b3a5db73b2f4e88310a5026..4bcc743edd7301b32c14559ad754d732ec1d08f3 100644
--- a/ui/gfx/compositor/compositor.h
+++ b/ui/gfx/compositor/compositor.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "base/memory/ref_counted.h"
+#include "base/observer_list.h"
 #include "ui/gfx/compositor/compositor_export.h"
 #include "ui/gfx/transform.h"
 #include "ui/gfx/native_widget_types.h"
@@ -20,6 +21,8 @@ class Rect;
 
 namespace ui {
 
+class CompositorObserver;
+
 struct TextureDrawParams {
   TextureDrawParams() : transform(), blend(false), compositor_size() {}
 
@@ -81,10 +84,10 @@ class COMPOSITOR_EXPORT Compositor : public base::RefCounted<Compositor> {
   virtual Texture* CreateTexture() = 0;
 
   // Notifies the compositor that compositing is about to start.
-  virtual void NotifyStart() = 0;
+  void NotifyStart();
 
   // Notifies the compositor that compositing is complete.
-  virtual void NotifyEnd() = 0;
+  void NotifyEnd();
 
   // Blurs the specific region in the compositor.
   virtual void Blur(const gfx::Rect& bounds) = 0;
@@ -102,15 +105,28 @@ class COMPOSITOR_EXPORT Compositor : public base::RefCounted<Compositor> {
   // Returns the size of the widget that is being drawn to.
   const gfx::Size& size() { return size_; }
 
+  // Layers do not own observers. It is the responsibility of the observer to
+  // remove itself when it is done observing.
+  void AddObserver(CompositorObserver* observer);
+  void RemoveObserver(CompositorObserver* observer);
+
  protected:
   explicit Compositor(const gfx::Size& size) : size_(size) {}
   virtual ~Compositor() {}
 
+  // Notifies the compositor that compositing is about to start.
+  virtual void OnNotifyStart() = 0;
+
+  // Notifies the compositor that compositing is complete.
+  virtual void OnNotifyEnd() = 0;
+
   virtual void OnWidgetSizeChanged() = 0;
 
  private:
   gfx::Size size_;
 
+  ObserverList<CompositorObserver> observer_list_;
+
   friend class base::RefCounted<Compositor>;
 };