Use log source for log reading

Change-Id: I4d6018a6117f5864cda38a5e6485c6d08a782999
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/events/logging/timestamp_extractor.cc b/aos/events/logging/timestamp_extractor.cc
index cf0ea5a..72f9de8 100644
--- a/aos/events/logging/timestamp_extractor.cc
+++ b/aos/events/logging/timestamp_extractor.cc
@@ -43,7 +43,7 @@
 
   // Now, build up the estimator used to solve for time.
   message_bridge::MultiNodeNoncausalOffsetEstimator multinode_estimator(
-      config, config, log_files.front_boots(), FLAGS_skip_order_validation,
+      config, config, log_files.boots(), FLAGS_skip_order_validation,
       chrono::seconds(0));
   multinode_estimator.set_reboot_found(
       [config](distributed_clock::time_point reboot_time,