[REF] small refactoring, it simplify the make_cells method in pivot.js (addon web_graph)
[REF] small refactoring, it simplify the make_cells method in pivot.js (addon web_graph)

havt/openerp-web,havt/openerp-web,havt/openerp-web,havt/openerp-web,havt/openerp-web