Handle errors within LogEvent

Errors are recorded within StatsdStats. The associated CL to change
stats_log.proto within google3 is at cr/306795778.

Test: adb shell dumpsys stats --metadata
Test: bit statsd_test:*
Bug: 144373276
Change-Id: Id80cace9350f77d64a2d401f7fac7b12501e82ee
diff --git a/cmds/statsd/src/stats_log.proto b/cmds/statsd/src/stats_log.proto
index ed98f50..b6f9014 100644
--- a/cmds/statsd/src/stats_log.proto
+++ b/cmds/statsd/src/stats_log.proto
@@ -422,6 +422,7 @@
     message AtomStats {
         optional int32 tag = 1;
         optional int32 count = 2;
+        optional int32 error_count = 3;
     }
 
     repeated AtomStats atom_stats = 7;
@@ -457,6 +458,7 @@
         optional int64 empty_data = 15;
         optional int64 registered_count = 16;
         optional int64 unregistered_count = 17;
+        optional int32 atom_error_count = 18;
     }
     repeated PulledAtomStats pulled_atom_stats = 10;