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

chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.h

Index: chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.h
diff --git a/chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.h b/chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.h
new file mode 100644
index 0000000000000000000000000000000000000000..793655a2f738a946c318acaa0f2ef334004163d6
--- /dev/null
+++ b/chrome/browser/chromeos/arc/tracing/arc_tracing_bridge.h
@@ -0,0 +1,62 @@
+// 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_TRACING_ARC_TRACING_BRIDGE_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_TRACING_ARC_TRACING_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/tracing/arc_tracing_agent.h"
+#include "components/arc/arc_service.h"
+#include "components/arc/common/tracing.mojom.h"
+#include "components/arc/instance_holder.h"
+
+namespace arc {
+
+class ArcBridgeService;
+
+// This class provides the interface to trigger tracing in the container.
+class ArcTracingBridge
+    : public ArcService,
+      public chromeos::ArcTracingAgent::Delegate,
+      public InstanceHolder<mojom::TracingInstance>::Observer {
+ public:
+  explicit ArcTracingBridge(ArcBridgeService* bridge_service);
+  ~ArcTracingBridge() override;
+
+  // InstanceHolder<mojom::TracingInstance>::Observer overrides:
+  void OnInstanceReady() override;
+
+  // chromeos::ArcTracingAgent::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_;
+
+  // NOTE: Weak pointers must be invalidated before all other member variables
+  // so it must be the last member.

[dcheng, 2017/03/10 22:09:24]

Nit: I don't think this comment is too useful (as the build will break if this
isn't true)

[Earl Ou, 2017/03/13 02:00:13]

In my local machine, the build will still success if the order is not correct,
and also many files in this codebase have this type of comments to avoid mistake
in the future modification. I think it's still worth to keep this.

+  base::WeakPtrFactory<ArcTracingBridge> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcTracingBridge);
+};
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_TRACING_ARC_TRACING_BRIDGE_H_