How to track the states of subtasks grouped by parent?

[Franck Thirouard]

For each story, I d'like to see the count of subtasks in each existing state.

For example:

----- -    |  To Do  | In Prog | Done

Story 1   |  -- 3 --  | -- 2 -- | -- 0 --

Story 2   | -- 2 -- | -- 1 -- | -- 1 --

I tried the two dimensional filter with Status as the X-axis dimension but I could not select Parent issue as a Y-axis dimension.

Any better idea?