vtkCocoaRenderWindow::Frame calls Render
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
In vtkCocoaRenderWindow::Frame, Render is sometimes called even when a recently rendered image is waiting to be displayed in the back buffer.
This is causing a failure of the LoadOpenGLExtension test (which has nothing to do with the loading of the extensions). See the dashboard tests for the Darwin-c++-cocoa build on krondor.kitware.