convert_inline relies on getComputedStyle to crystalize var and calc
values. This however was conflicting with the fact that it also combines
positional styles (eg., margin-top, padding-left) together. This seems
to make getComputedStyle give out the wrong value with var and calc.

closes odoo/odoo#98003

Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>