Implement wxAppProgressIndicator.

An helper class used for updating the progress of taskbar button.

Author: Chaobin Zhang

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77612 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/taskbarbutton.h

@@ -45,6 +45,7 @@ public:
 private:
     friend class wxFrame;
     friend class wxThumbBarButton;
+    friend class wxAppProgressIndicator;
 
     wxTaskBarButtonImpl(WXWidget parent);