[tp] Export upid in exp_thread_slice
[tp] Export upid in exp_thread_slice

R=lalitm@google.com

Change-Id: I2456bde996a6759349cd1cca7c6a0988c74c77d1
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto