arc: enable Android tracing in verified-boot mode

chromeos/trace/arc_trace_agent.h

Index: chromeos/trace/arc_trace_agent.h
diff --git a/chromeos/trace/arc_trace_agent.h b/chromeos/trace/arc_trace_agent.h
new file mode 100644
index 0000000000000000000000000000000000000000..844b7190f81c3ed29a59f5d1a4d7b5db2ea2a883
--- /dev/null
+++ b/chromeos/trace/arc_trace_agent.h
@@ -0,0 +1,37 @@
+// Copyright 2016 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.
+
+#ifndef CHROMEOS_TRACE_ARC_TRACE_AGENT_H_
+#define CHROMEOS_TRACE_ARC_TRACE_AGENT_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/trace_event/trace_event.h"
+#include "base/trace_event/tracing_agent.h"
+#include "chromeos/chromeos_export.h"
+
+namespace chromeos {
+
+// A wrapper for controlling tracing in ARC container.
+class CHROMEOS_EXPORT ArcTraceAgent : public base::trace_event::TracingAgent {
+ public:
+  class Delegate {
+   public:

[Yusuke Sato, 2017/01/17 22:17:21]

add
 virtual ~Delegate() = default;
to force the derived class(es)' destructor(s) to be virtual?

[Earl Ou, 2017/01/18 09:13:21]

Done.

+    virtual void StartTracing(
+        const base::trace_event::TraceConfig& trace_config,
+        const base::Callback<void(bool)>& callback) = 0;

[Luis Héctor Chávez, 2017/01/17 19:20:32]

nit: Can you add something like

using StartTracingCallback = base::Callback<void(bool)>;

? same for the one in StopTracing.

[Earl Ou, 2017/01/18 09:13:21]

Done.

+
+    virtual void StopTracing(
+        const base::Callback<void(const std::string&)>& callback) = 0;
+  };
+
+  static ArcTraceAgent* GetInstance();
+

[Yusuke Sato, 2017/01/17 22:17:21]

add
 virtual ~ArcTraceAgent() = default;
?

[Earl Ou, 2017/01/18 09:13:21]

Done.

+  virtual void SetDelegate(Delegate* delegate) = 0;

[Yusuke Sato, 2017/01/17 22:17:21]

Please add a function document. What happens if |delegate| is nullptr, for
example?

[Earl Ou, 2017/01/18 09:13:21]

Done.

+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_TRACE_ARC_TRACE_AGENT_H_