perf hists browser: Take the --comm, --dsos, etc filters into account

At some point:

  commit 2c86c7ca
  Author: Namhyung Kim <namhyung@kernel.org>
  Date:   Mon Mar 17 18:18:54 2014 -0300

    perf report: Merge al->filtered with hist_entry->filtered

We stopped dropping samples for things filtered via the --comms, --dsos,
--symbols, etc, i.e. things marked as filtered in the symbol resolution
routines (thread__find_addr_map(), perf_event__preprocess_sample(),
etc).

But then, in:

  commit 268397cb


  Author: Namhyung Kim <namhyung@kernel.org>
  Date:   Tue Apr 22 14:49:31 2014 +0900

    perf top/tui: Update nr_entries properly after a filter is applied

We don't take into account entries that were filtered in
perf_event__preprocess_sample() and friends, which leads to
inconsistency in the browser seek routines, that expects the number of
hist_entry->filtered entries to match what it thinks is the number of
unfiltered, browsable entries.

So, for instance, when we do:

  perf top --symbols ___non_existent_symbol___

the hist_browser__nr_entries() routine thinks there are no filters in
place, uses the hists->nr_entries but all entries are filtered, leading
to a segfault.

Tested with:

   perf top --symbols malloc,free --percentage=relative

Freezing, by pressing 'f', at any time and doing the math on the
percentages ends up with 100%, ditto for:

   perf top --dsos libpthread-2.20.so,libxul.so --percentage=relative

Both were segfaulting, all fixed now.

More work needed to do away with checking if filters are in place, we
should just use the nr_non_filtered_samples counter, no need to
conditionally use it or hists.nr_filter, as what the browser does is
just show unfiltered stuff. An audit of how it is being accounted is
needed, this is the minimal fix.

Reported-by: Michael Petlan <mpetlan@redhat.com>
Fixes: 268397cb

 ("perf top/tui: Update nr_entries properly after a filter is applied")
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-6w01d5q97qk0d64kuojme5in@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>