perf gtk/hists: Set rules hint for the hist browser

The 'rules' means that every second line of the tree view has a shaded
background, which makes it easier to see which cell belongs to which
row in the tree view.  It can be useful for a tree view that has a lot
of rows.

Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
1 file changed