arc: enable Android tracing from chrome://tracing in dev mode

chrome/browser/chromeos/arc/trace/arc_trace_bridge.h

+// 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 CHROME_BROWSER_CHROMEOS_ARC_TRACE_ARC_TRACE_BRIDGE_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_TRACE_ARC_TRACE_BRIDGE_H_
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/trace_event/trace_event.h"
+#include "chromeos/trace/arc_trace_agent.h"
+#include "components/arc/arc_service.h"
+#include "components/arc/common/trace.mojom.h"
+#include "components/arc/instance_holder.h"
+
+namespace arc {
+
+class ArcBridgeService;
+
+// This class provides the interface to trigger tracing in the container.
+class ArcTraceBridge : public ArcService,
+                       public chromeos::ArcTraceAgent::Delegate,
+                       public InstanceHolder<mojom::TraceInstance>::Observer {
+ public:
+  explicit ArcTraceBridge(ArcBridgeService* bridge_service);
+  ~ArcTraceBridge() override;
+
+  // InstanceHolder<mojom::TraceInstance>::Observer overrides:
+  void OnInstanceReady() override;
+
+  // chromeos::ArcTraceAgent::Delegate overrides:
+  void StartTracing(const base::trace_event::TraceConfig& trace_config,
+                    const StartTracingCallback& callback) override;
+  void StopTracing(const StopTracingCallback& callback) override;
+
+ private:
+  struct Category {
+    // The name used by Android to trigger tracing.
+    const std::string name;
+    // The full name shown in the tracing UI in chrome://tracing.
+    const std::string full_name;
+  };
+  // Callback for QueryAvailableCategories.
+  void OnCategoriesReady(const std::vector<std::string>& categories);
+
+  // List of available categories.
+  std::vector<Category> categories_;
+  base::WeakPtrFactory<ArcTraceBridge> weak_ptr_factory_;

[Yusuke Sato, 2017/03/06 02:09:13]

nit: can you add a comment like this?

// NOTE: Weak pointers must be invalidated before all other member variables.

[Earl Ou, 2017/03/06 05:38:10]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(ArcTraceBridge);
+};
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_TRACE_ARC_TRACE_BRIDGE_H_