Write test for exporting data labels in area chart for OOXML.

Change-Id: Icbb17f56643f7d89bf739b0f218b2ca8a6309d9a
Fix the test. It's bar3DChart not barChart.

Change-Id: I8e504dfee81557a1965bb4bbce4ea975c13fe775
Area chart also doesn't support label position property.

Change-Id: I612ca7426b2b3de07d4afe1d78cd809f1f6b37bb