perf diff: Support --pid/--tid filter options

Using the existing symbol_conf.pid_list_str and symbol_conf.tid_list_str
logic.

For example:

perf diff --tid 13965

It'll only diff the samples for thread 13965.

Signed-off-by: Jin Yao <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Jin Yao <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-diff.txt

···
 	CPUs are specified with -: 0-2. Default is to report samples on all
 	CPUs.
 
+--pid=::
+	Only diff samples for given process ID (comma separated list).
+
+--tid=::
+	Only diff samples for given thread ID (comma separated list).
+
 COMPARISON
 ----------
 The comparison is governed by the baseline file. The baseline perf.data

tools/perf/builtin-diff.c

···
 	OPT_STRING(0, "time", &pdiff.time_str, "str",
 		   "Time span (time percent or absolute timestamp)"),
 	OPT_STRING(0, "cpu", &cpu_list, "cpu", "list of cpus to profile"),
+	OPT_STRING(0, "pid", &symbol_conf.pid_list_str, "pid[,pid...]",
+		   "only consider symbols in these pids"),
+	OPT_STRING(0, "tid", &symbol_conf.tid_list_str, "tid[,tid...]",
+		   "only consider symbols in these tids"),
 	OPT_END()
 };