[BattOr] Make BattOr able to return firmware version.

tools/battor_agent/battor_agent.cc

Index: tools/battor_agent/battor_agent.cc
diff --git a/tools/battor_agent/battor_agent.cc b/tools/battor_agent/battor_agent.cc
index 6fc6ea17983b09ed662e617b9906fc6c3dbc2f94..3c4456fb051e3051b2ae1c70a93f390747269629 100644
--- a/tools/battor_agent/battor_agent.cc
+++ b/tools/battor_agent/battor_agent.cc
@@ -159,6 +159,12 @@ void BattOrAgent::RecordClockSyncMarker(const std::string& marker) {
   PerformAction(Action::REQUEST_CONNECTION);
 }
 
+int BattOrAgent::Version() {
+  DCHECK(thread_checker_.CalledOnValidThread());

[charliea (OOO until 10-5), 2016/10/04 15:15:48]

So after you make this look like:

void BattOrAgent::GetVersion() {
   ...
}

I think the key thing that's not right here yet is that we need to actually
*get* the EEPROM from the BattOr before we're able to look up the version number
in it. The EEPROM is basically just a struct that we request from the BattOr and
the BattOr sends back. However, in order to even perform that request, we need
to initialize the connection with the BattOr. You can copy how to do this from
StartTracing, StopTracing, and RecordClockSyncMarker.

After the connection is initialized, OnConnectionOpened() will be called. You'll
probably want to add an additional case in the switch statement there along the
lines of:

case Command::GET_VERSION:
  PerformAction(Action::SEND_EEPROM_REQUEST);
  return;

Then, after you receive the EEPROM (in the switch() statement of
BattOrAgent::OnBytesRead, under Action::READ_EEPROM), you'll want to add some
logic along the lines of 

if (command_ == Command::GET_VERSION) {
  CompleteCommand(BATTOR_ERROR_NONE);
} else if (command_ == Command::STOP_TRACING) {
  // Existing logic...
} else {
  // Throw some error
}

Finally, you'll want to add your battor_eeprom_->version lookup logic that you
have right below into CompleteCommand under a new GET_VERSION section.
CompleteCommand is basically called to say "we have all the information that we
need from the BattOr stored in member variables of the BattOrAgent: go ahead and
call the callback with the right info".

+  return 1; // Actually return here.
+  return battor_eeprom_->version;
+}
+
 void BattOrAgent::BeginConnect() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
@@ -187,6 +193,8 @@ void BattOrAgent::OnConnectionOpened(bool success) {
     case Command::RECORD_CLOCK_SYNC_MARKER:
       PerformAction(Action::SEND_CURRENT_SAMPLE_REQUEST);
       return;
+    case Command::VERSION:
+      return;
     case Command::INVALID:
       NOTREACHED();
   }
@@ -530,6 +538,10 @@ void BattOrAgent::CompleteCommand(BattOrError error) {
           FROM_HERE, base::Bind(&Listener::OnRecordClockSyncMarkerComplete,
                                 base::Unretained(listener_), error));
       break;
+    case Command::VERSION:
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE, base::Bind(&Listener::OnGetVersionComplete,
+                                base::Unretained(listener_), error));
     case Command::INVALID:
       NOTREACHED();
   }