Changes view manager to report visibility and drawn state

mojo/services/view_manager/server_view_delegate.h

Index: mojo/services/view_manager/server_view_delegate.h
diff --git a/mojo/services/view_manager/server_view_delegate.h b/mojo/services/view_manager/server_view_delegate.h
index f110ec8e3646f04780e64b3d00ab23f780f694cc..bc83d63511e1e69b4ef42f3a8c656f75d2711cd6 100644
--- a/mojo/services/view_manager/server_view_delegate.h
+++ b/mojo/services/view_manager/server_view_delegate.h
@@ -22,7 +22,10 @@ class MOJO_VIEW_MANAGER_EXPORT ServerViewDelegate {
   // the hierarchy).
   virtual void OnViewDestroyed(const ServerView* view) = 0;
 
-  // Invoked when the hierarchy has changed.
+  virtual void OnWillChangeViewHierarchy(const ServerView* view,
+                                         const ServerView* new_parent,
+                                         const ServerView* old_parent) = 0;
+
   virtual void OnViewHierarchyChanged(const ServerView* view,
                                       const ServerView* new_parent,
                                       const ServerView* old_parent) = 0;
@@ -33,6 +36,8 @@ class MOJO_VIEW_MANAGER_EXPORT ServerViewDelegate {
 
   virtual void OnViewBitmapChanged(const ServerView* view) = 0;
 
+  virtual void OnWillChangeViewVisibility(const ServerView* view) = 0;
+
  protected:
   virtual ~ServerViewDelegate() {}
 };