pw_bloat: Fix default data source

pwrev/108912 accidentally changed the default data sources provided to
bloaty in bloat.py, breaking some size reports. This reverts that to the
intended list.

Change-Id: I2abcaa8def9b301c61a486a7b86fbcca1e268da1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/112312
Pigweed-Auto-Submit: Alexei Frolov <frolv@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
diff --git a/pw_bloat/py/pw_bloat/bloat.py b/pw_bloat/py/pw_bloat/bloat.py
index 802ad2d..49b35cd 100755
--- a/pw_bloat/py/pw_bloat/bloat.py
+++ b/pw_bloat/py/pw_bloat/bloat.py
@@ -201,7 +201,7 @@
                                     gn_arg_dict['out_dir'], data_sources,
                                     extra_args)
 
-    default_data_sources = ['symbols']
+    default_data_sources = ['segment_names', 'symbols']
 
     diff_report = ''
     rst_diff_report = ''