Adds View::visible() and IsDrawn

mojo/services/public/cpp/view_manager/view_observer.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_OBSERVER_H_
 #define MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_OBSERVER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 46 matching lines @@
                                     const gfx::Rect& old_bounds,
                                     const gfx::Rect& new_bounds) {}
   virtual void OnViewBoundsChanged(View* view,
                                    const gfx::Rect& old_bounds,
                                    const gfx::Rect& new_bounds) {}
 
   virtual void OnViewFocusChanged(View* gained_focus, View* lost_focus) {}
 
   virtual void OnViewInputEvent(View* view, const EventPtr& event) {}
 
+  virtual void OnViewVisibilityChanging(View* view) {}
+  virtual void OnViewVisibilityChanged(View* view) {}
+
+  // Sent when the drawn state changes. This is only sent for the root nodes
+  // when embedded.
+  virtual void OnViewDrawnChanging(View* view) {}
+  virtual void OnViewDrawnChanged(View* view) {}
+
  protected:
   virtual ~ViewObserver() {}
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_VIEW_OBSERVER_H_