Fix bug in summary trace to text.

Trace to text summary now counts tids without any child threads.

Change-Id: I7a7c38403f9d96cb8dbf6f176d2c9d2a4cca8a57
diff --git a/tools/trace_to_text/main.cc b/tools/trace_to_text/main.cc
index bd29756..ad82d5d 100644
--- a/tools/trace_to_text/main.cc
+++ b/tools/trace_to_text/main.cc
@@ -350,6 +350,7 @@
         if (packet.has_process_tree()) {
           const ProcessTree& tree = packet.process_tree();
           for (Process process : tree.processes()) {
+            tids_in_tree.insert(process.pid());
             for (ProcessTree::Thread thread : process.threads()) {
               tids_in_tree.insert(thread.tid());
             }