arc: enable Android tracing from chrome://tracing in dev 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..32e8fed8da82f9534531e262f544b785b80f16d1
--- /dev/null
+++ b/chromeos/trace/arc_trace_agent.h
@@ -0,0 +1,47 @@
+// Copyright 2017 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 "base/callback_forward.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.
+// The overriden Stop/StartAgentTracing functions are implemented by the
+// Delegate object to interact with ARC bridge. All the functions are expected
+// to be called on the brower's UI thread.
+class CHROMEOS_EXPORT ArcTraceAgent : public base::trace_event::TracingAgent {
+ public:
+  class Delegate {
+   public:
+    using StartTracingCallback = base::Callback<void(bool)>;
+    using StopTracingCallback = base::Callback<void(bool)>;
+
+    virtual ~Delegate();
+
+    virtual void StartTracing(
+        const base::trace_event::TraceConfig& trace_config,
+        const StartTracingCallback& callback) = 0;
+
+    virtual void StopTracing(const StopTracingCallback& callback) = 0;
+  };
+
+  virtual ~ArcTraceAgent();
+
+  static ArcTraceAgent* GetInstance();
+
+  // Sets Delegate instance, which should implement the communication
+  // using ARC bridge. If set to nullptr, calling of Start/StopAgentTracing
+  // does nothing.
+  virtual void SetDelegate(Delegate* delegate) = 0;
+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_TRACE_ARC_TRACE_AGENT_H_