logd: add locks around ~SerializedFlushToState

This accesses shared resources in SerializedLogBuffer and therefore
requires a lock.

Bug: 169736426
Test: malloc_debug_system_tests
Change-Id: I807c65f4719481f933b4917a50f83f933b1929fb
diff --git a/logd/SerializedLogBuffer.h b/logd/SerializedLogBuffer.h
index 294cfe6..9164526 100644
--- a/logd/SerializedLogBuffer.h
+++ b/logd/SerializedLogBuffer.h
@@ -42,6 +42,7 @@
     int Log(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid, pid_t tid, const char* msg,
             uint16_t len) override;
     std::unique_ptr<FlushToState> CreateFlushToState(uint64_t start, LogMask log_mask) override;
+    void DeleteFlushToState(std::unique_ptr<FlushToState> state) override;
     bool FlushTo(LogWriter* writer, FlushToState& state,
                  const std::function<FilterResult(log_id_t log_id, pid_t pid, uint64_t sequence,
                                                   log_time realtime)>& filter) override;