[BattOr] Make BattOr able to return firmware version.

tools/battor_agent/battor_agent.h

Index: tools/battor_agent/battor_agent.h
diff --git a/tools/battor_agent/battor_agent.h b/tools/battor_agent/battor_agent.h
index 810df26936af2cf15d4c72845937aa7fac8da676..4ebacf819905c2491c18d662f8c407c6aa76bd62 100644
--- a/tools/battor_agent/battor_agent.h
+++ b/tools/battor_agent/battor_agent.h
@@ -43,6 +43,7 @@ class BattOrAgent : public BattOrConnection::Listener,
     virtual void OnStopTracingComplete(const std::string& trace,
                                        BattOrError error) = 0;
     virtual void OnRecordClockSyncMarkerComplete(BattOrError error) = 0;
+    virtual void OnGetVersionComplete(const int version, BattOrError error) = 0;
   };
 
   BattOrAgent(
@@ -66,6 +67,7 @@ class BattOrAgent : public BattOrConnection::Listener,
   void OnMessageRead(bool success,
                      BattOrMessageType type,
                      std::unique_ptr<std::vector<char>> bytes) override;
+  int Version();
 
  protected:
   // The connection that knows how to communicate with the BattOr in terms of
@@ -85,6 +87,7 @@ class BattOrAgent : public BattOrConnection::Listener,
     START_TRACING,
     STOP_TRACING,
     RECORD_CLOCK_SYNC_MARKER,
+    VERSION,
   };
 
   enum class Action {