Stocks app shouldn't show black when resuming from recents list

sky/shell/ui_delegate.h

Index: sky/shell/ui_delegate.h
diff --git a/sky/shell/ui_delegate.h b/sky/shell/ui_delegate.h
index d50a34acdf421b329ba7f480f4dbd4114719196a..7c8368a8b31392025b8ff98a3f010ccc29e8805a 100644
--- a/sky/shell/ui_delegate.h
+++ b/sky/shell/ui_delegate.h
@@ -8,6 +8,7 @@
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "sky/services/viewport/viewport_observer.mojom.h"
 #include "ui/gfx/geometry/size.h"
+#include "ui/gfx/native_widget_types.h"
 
 namespace sky {
 namespace shell {
@@ -16,6 +17,8 @@ class UIDelegate {
  public:
   virtual void ConnectToViewportObserver(
       mojo::InterfaceRequest<ViewportObserver> request) = 0;
+  virtual void OnAcceleratedWidgetAvailable(gfx::AcceleratedWidget widget) = 0;
+  virtual void OnOutputSurfaceDestroyed() = 0;
 
  protected:
   virtual ~UIDelegate();