Code review comment for lp:~attente/mir/basic-menu-surface-position

1. Doesn't compile - see below
2. Is wrong - the placement should be relative to the parent window

[ 34%] Building CXX object src/server/shell/CMakeFiles/mirshell.dir/default_placement_strategy.cpp.o
/mir/src/server/shell/default_placement_strategy.cpp: In member function 'virtual mir::scene::SurfaceCreationParameters mir::shell::DefaultPlacementStrategy::place(const mir::scene::Session&, const mir::scene::SurfaceCreationParameters&)':
/mir/src/server/shell/default_placement_strategy.cpp:46:27: error: 'struct mir::scene::SurfaceCreationParameters' has no member named 'attachment_rect'
     if (placed_parameters.attachment_rect.is_set())
                           ^
/mir/src/server/shell/default_placement_strategy.cpp:47:54: error: 'struct mir::scene::SurfaceCreationParameters' has no member named 'attachment_rect'
       placed_parameters.top_left = placed_parameters.attachment_rect.value().bottom_left();
                                                      ^
src/server/shell/CMakeFiles/mirshell.dir/build.make:54: recipe for target 'src/server/shell/CMakeFiles/mirshell.dir/default_placement_strategy.cpp.o' failed
make[2]: *** [src/server/shell/CMakeFiles/mirshell.dir/default_placement_strategy.cpp.o] Error 1
CMakeFiles/Makefile2:3151: recipe for target 'src/server/shell/CMakeFiles/mirshell.dir/all' failed