tp: fix nest count handling for async slices

This CL fixes the quite broken state of nest counts for async slices. We
didn't notice this until now as we only ever used legacy unnestable
slices but as we're now using unnestable slices moving forward, we need
to fix this.

Change-Id: If559f8fcfb3d64078c2ff88301dd2e9950aa36d9
diff --git a/Android.bp b/Android.bp
index eb4a59c..9516297 100644
--- a/Android.bp
+++ b/Android.bp
@@ -7480,6 +7480,7 @@
     "src/trace_processor/importers/memory_tracker/graph_unittest.cc",
     "src/trace_processor/importers/memory_tracker/raw_process_memory_node_unittest.cc",
     "src/trace_processor/importers/proto/args_table_utils_unittest.cc",
+    "src/trace_processor/importers/proto/async_track_set_tracker_unittest.cc",
     "src/trace_processor/importers/proto/heap_graph_tracker_unittest.cc",
     "src/trace_processor/importers/proto/heap_profile_tracker_unittest.cc",
     "src/trace_processor/importers/proto/proto_trace_parser_unittest.cc",