Rename log file header to monotonic_start_time

monotonic_sent_time is not the right term.  Before we propegate this
further, lets rename it.

Change-Id: I5df2e5aecdd751d46c4d22346738e9925c4885e9
diff --git a/aos/events/logging/BUILD b/aos/events/logging/BUILD
index 96ef288..3df5592 100644
--- a/aos/events/logging/BUILD
+++ b/aos/events/logging/BUILD
@@ -7,6 +7,7 @@
     includes = [
         "//aos:configuration_fbs_includes",
     ],
+    visibility = ["//visibility:public"],
 )
 
 cc_library(
diff --git a/aos/events/logging/logger.cc b/aos/events/logging/logger.cc
index 9968b80..584c68d 100644
--- a/aos/events/logging/logger.cc
+++ b/aos/events/logging/logger.cc
@@ -137,11 +137,11 @@
                                                                polling_period)
               .count());
 
-      log_file_header_builder.add_monotonic_sent_time(
+      log_file_header_builder.add_monotonic_start_time(
           std::chrono::duration_cast<std::chrono::nanoseconds>(
               monotonic_now.time_since_epoch())
               .count());
-      log_file_header_builder.add_realtime_sent_time(
+      log_file_header_builder.add_realtime_start_time(
           std::chrono::duration_cast<std::chrono::nanoseconds>(
               realtime_now.time_since_epoch())
               .count());
@@ -381,13 +381,13 @@
 monotonic_clock::time_point LogReader::monotonic_start_time() {
   return monotonic_clock::time_point(std::chrono::nanoseconds(
       flatbuffers::GetSizePrefixedRoot<LogFileHeader>(configuration_.data())
-          ->monotonic_sent_time()));
+          ->monotonic_start_time()));
 }
 
 realtime_clock::time_point LogReader::realtime_start_time() {
   return realtime_clock::time_point(std::chrono::nanoseconds(
       flatbuffers::GetSizePrefixedRoot<LogFileHeader>(configuration_.data())
-          ->realtime_sent_time()));
+          ->realtime_start_time()));
 }
 
 void LogReader::Register(EventLoop *event_loop) {
diff --git a/aos/events/logging/logger.fbs b/aos/events/logging/logger.fbs
index 5d6aa0a..3e89ff3 100644
--- a/aos/events/logging/logger.fbs
+++ b/aos/events/logging/logger.fbs
@@ -15,9 +15,9 @@
 
 table LogFileHeader {
   // Time this log file started on the monotonic clock in nanoseconds.
-  monotonic_sent_time:long;
+  monotonic_start_time:long;
   // Time this log file started on the realtime clock in nanoseconds.
-  realtime_sent_time:long;
+  realtime_start_time:long;
 
   // Messages are not written in order to disk.  They will be out of order by
   // at most this duration (in nanoseconds).  If the log reader buffers until