Anti-aliasing stops working for QOpenGLWidget if the parent of the QOpenGLWidget is changed and the former parent is shown

A parent-changing maneuver reveals the faulty behavior. Qt 5.10 alpha seems to fix this.

Steps to reproduce:

• Run the sample attached
• Observe and compare the red lines
  EXPECTED: Anti-aliasing should be applied to the lines in both QOpenGLWidgets
  ACTUAL: Anti-aliasing is not applied to the QOpenGLWidget that has a visible former parent