[IMP]use CompoundContext class.

bzr revid: vme@tinyerp.com-20120111052401-5vvf6aggna5nfykl

diff --cc addons/web/static/src/js/view_form.js
index 818c506,2d0cf21..93502fb
--- 1/addons/web/static/src/js/view_form.js
--- 2/addons/web/static/src/js/view_form.js
+++ b/addons/web/static/src/js/view_form.js
@@@ -252,8 -255,7 +255,8 @@@ openerp.web.FormView = openerp.web.View
              'None': function () {return null;},
              'context': function (i) {
                  context_index = i;
 -                var ctx = widget.build_context ? widget.build_context() : {};
 +                var ctx = widget.build_context ?
-                     _.extend(widget.build_context(),self.dataset.context):{};
++                    new openerp.web.CompoundContext(widget.build_context(),self.dataset.get_context()):{};
                  return ctx;
              }
          };