QOpenGLWidget does not update when content changed while its hidden

Due to change in https://codereview.qt-project.org/#/c/141307/ when a QOpenGLWidget content is updated while its hidden, the correct content will not be shown when the widget is made visible after. This is because, the new variable 

renderToTextureReallyDirty

is never set to true when it is updated while the widget is hidden.

Attached is a test app to repo the issue. Please follow these steps to see the issue mentioned

1) Click on the button and notice the red rectangle will change position on every click. The label below indicates the corner position of the rectangle

2) Now, uncheck the checkbox and notice QOpenGLWidget will be hidden.

3) Now click the button again so that the rect position will be changed. Ensure its not the same position before the widget was made hidden by looking at the label

4) Now check on the checkbox and notice the red rectangle's position never got updated to the one indicated by the label

And here is the patch I used to make it work

qtOpenGlWidget.diff