rendercontext: Improve comboboxes in the double-buffered toolbar.
rendercontext: Improve comboboxes in the double-buffered toolbar.

Change-Id: I91bfb4ea4672ff09482679f8fcf18a65e5a6ee3c

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core