The abort happened when a query contained a conjunctive predicate
of the form 'view column = constant' in the WHERE condition and 
the grouping list also contained a reference to a view column yet
a different one.

Removed the failing assertion as invalid in a general case.

Also fixed a bug that prevented applying some optimization for grouping
queries using views. If the WHERE condition of such a query contains
a conjunctive condition of the form 'view column = constant' and
this view column is used in the grouping list then grouping by this
column can be eliminated. The bug blocked performing this elimination.


mysql-test/r/view.result:
  Added a test case for bug #29104.
mysql-test/t/view.test:
  Added a test case for bug #29104.
sql/item.cc:
  Fixed bug #29104: assertion abort for grouping queries using views.
  The abort happened when a query contained a conjunctive predicate
  of the form 'view column = constant' in the WHERE condition and 
  the grouping list also contained a reference to a view column yet
  a different one.
  
  Removed the failing assertion as invalid in a general case.
  
  Also fixed a bug that prevented applying some optimization for grouping
  queries using views. If the WHERE condition of such a query contains
  a conjunctive condition of the form 'view column = constant' and
  this view column is used in the grouping list then grouping by this
  column can be eliminated. The bug blocked performing this elimination.
  This bug was in the function Item_field::eq while the failing
  assertion was in the function Item_direct_view_ref::eq.