After we use the filters to zoom into DSOs or threads, we can use <-
(left arrow) to zoom out from the last filter applied.

It is still possible to zoom out of order by using the popup menu.

With this we now have the zoom out operation on the browsing fast path,
by allowing fast navigation using just the four arrors and the enter key
to expand collapse callchains.
Suggested-by: Ingo Molnar <mingo@elte.hu>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>