[INTERNAL] m.ComboBox: adds the role combobox to the control's root
element

In IE browsers, JAWS 15.0 announce the ComboBox only if the
role combobox is set to the control's root element.

Change-Id: I946d2be54855d3af4fabc7a9ecaf2d8654d7736c
Merge "[INTERNAL] m.ComboBox: adds the role combobox to the control's root element"