Remove old-format PersistedLogs support

components/metrics/persisted_logs.h

Index: components/metrics/persisted_logs.h
diff --git a/components/metrics/persisted_logs.h b/components/metrics/persisted_logs.h
index 2af474bb341964162a8a684cbf834a96e2c7ceeb..18a80008dbea37c5eda518c9584589f161a16a1e 100644
--- a/components/metrics/persisted_logs.h
+++ b/components/metrics/persisted_logs.h
@@ -55,7 +55,6 @@ class PersistedLogs {
   PersistedLogs(std::unique_ptr<PersistedLogsMetrics> metrics,
                 PrefService* local_state,
                 const char* pref_name,
-                const char* outdated_pref_name,
                 size_t min_log_count,
                 size_t min_log_bytes,
                 size_t max_log_size);
@@ -111,9 +110,6 @@ class PersistedLogs {
   // Reads the list from the ListValue.
   LogReadStatus ReadLogsFromPrefList(const base::ListValue& list);
 
-  // Reads the list from the ListValue in the old Log-hash pair format.
-  LogReadStatus ReadLogsFromOldFormatPrefList(const base::ListValue& list);
-
   // An object for recording UMA metrics.
   std::unique_ptr<PersistedLogsMetrics> metrics_;
 
@@ -125,10 +121,6 @@ class PersistedLogs {
   // The name of the preference to serialize logs to/from.
   const char* pref_name_;
 
-  // The name of the preference to serialize logs to/from which may contain log
-  // in the old formatting.
-  const char* outdated_pref_name_;
-
   // We will keep at least this |min_log_count_| logs or |min_log_bytes_| bytes
   // of logs, whichever is greater, when writing to disk.  These apply after
   // skipping logs greater than |max_log_size_|.