Trace-based benchmarking via a mojo app.

apps/benchmark/trace_collector_client.h

Index: apps/benchmark/trace_collector_client.h
diff --git a/apps/benchmark/trace_collector_client.h b/apps/benchmark/trace_collector_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..3e5ba3718f5364847766a4f8bdcf8c30a01d4b10
--- /dev/null
+++ b/apps/benchmark/trace_collector_client.h
@@ -0,0 +1,49 @@
+// 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.
+
+#ifndef APPS_BENCHMARK_TRACE_COORDINATOR_CLIENT_H_
+#define APPS_BENCHMARK_TRACE_COORDINATOR_CLIENT_H_
+
+#include <memory>
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "mojo/data_pipe_utils/data_pipe_drainer.h"
+#include "mojo/services/tracing/public/interfaces/tracing.mojom.h"
+
+// Connects to trace collector in tracing.mojo to get traces and returns the
+// results as a single string to the receiver.
+class TraceCollectorClient : public mojo::common::DataPipeDrainer::Client {
+ public:
+  class Receiver {
+   public:
+    // |trace_data| will be a JSON list of the collected trace events.
+    virtual void OnTraceCollected(std::string trace_data) = 0;
+
+   protected:
+    virtual ~Receiver() {}
+  };
+
+  TraceCollectorClient(Receiver* receiver,
+                       tracing::TraceCollectorPtr collector);
+  ~TraceCollectorClient() override;
+
+  void Start(const std::string& categories);
+  void Stop();
+
+ private:
+  // mojo::common:DataPipeDrainer:
+  void OnDataAvailable(const void* data, size_t num_bytes) override;
+  void OnDataComplete() override;
+
+  Receiver* receiver_;
+  tracing::TraceCollectorPtr collector_;
+  scoped_ptr<mojo::common::DataPipeDrainer> drainer_;
+  std::string trace_data_;
+  bool currently_tracing_;
+
+  DISALLOW_COPY_AND_ASSIGN(TraceCollectorClient);
+};
+
+#endif  // APPS_BENCHMARK_TRACE_COORDINATOR_CLIENT_H_