simplify drawing of splitter, add more flat look
simplify drawing of splitter, add more flat look

Change-Id: Ie5040c2932715b2505635ff3cb909ccfeb4b7fa0

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