title: QComboBox can't change border color
body: <p>I have a class which inherits QComboBox. I need to set red border for this widget.<br>
  I can't use QPalette, I am trying to use setStyleSheet:<br>
  <code>pComboBox-&gt;setStyleSheet("QFrame { border: 2px solid red; }")</code><br>
  It works fine for QLineEdit, but for QComboBox I got red border around popup view and not combo box.<br>
  How can I get access to the frame of QComboBox?</p>