Gradient style is not available for ChartArea in Apex

[surendran-180202]

Apex chart background color: we need apply the gradient style color for entier 'Chart Area '.

We could not find the 'gradient' features in 'ChartArea' level. However, we can apply only the gradient style in the 'series level'.

Could you please help us to solve this problem?

Gradient Style-DiagonalLeft

Gradient Style DiagonalRight