Makes the BattOrAgent asynchronous

tools/battor_agent/battor_agent.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/battor_agent/battor_agent.h"
 
 #include <iostream>
 
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+
 namespace battor {
 
 BattOrAgent::BattOrAgent(const std::string& path) : path_(path) {
   // TODO: Open up a serial connection with the BattOr.

[Zhen Wang, 2015/10/30 16:46:44]

TODO(charliea)

Same for other places.

[charliea (OOO until 10-5), 2015/10/30 17:37:42]

Done.

 }
 
 BattOrAgent::~BattOrAgent() {
   // TODO: Close the serial connection with the BattOr.
 }
 
 void BattOrAgent::StartTracing() {
   // TODO: Tell the BattOr to start tracing.
 }
 
-void BattOrAgent::StopTracing(std::string* out_trace) {
+void BattOrAgent::StopTracing(std::string* trace_output,
+                              const base::Closure& callback) {
   // TODO: Tell the BattOr to stop tracing.
+  *trace_output = "battor trace output";
+  callback.Run();
 }
 
-void BattOrAgent::RecordClockSyncMarker(const std::string& marker) {
+void BattOrAgent::RecordClockSyncMarker(const std::string& marker,
+                                        const base::Closure& callback) {
   // TODO: Tell the BattOr to record the specified clock sync marker.
+  callback.Run();
 }
 
 void BattOrAgent::IssueClockSyncMarker() {
   // TODO: Tell atrace to issue a clock sync marker.
 }
 
 }  // namespace battor