Implements Windows system tracing.

content/browser/tracing/tracing_consumer_win.h

+// Copyright 2014 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 CONTENT_BROWSER_TRACING_TRACING_CONSUMER_WIN_H_
+#define CONTENT_BROWSER_TRACING_TRACING_CONSUMER_WIN_H_
+
+#include "base/bind.h"
+#include "base/memory/ref_counted_memory.h"
+#include "base/threading/thread.h"
+#include "base/values.h"
+#include "base/win/event_trace_consumer.h"
+#include "base/win/event_trace_controller.h"
+
+namespace content {
+
+class EtwSystemEventConsumer :
+    public base::win::EtwTraceConsumerBase<EtwSystemEventConsumer> {
+ public:
+  typedef base::Callback<void(const scoped_refptr<base::RefCountedString>&)>
+      OutputCallback;
+
+  // Constructor.
+  EtwSystemEventConsumer();

[nduca, 2014/02/20 07:04:54]

if its a singleton the constructor should be private and only Get should do it.
using the singleton pattern makes this work.

[etienneb, 2014/02/20 19:08:03]

Done.

+

[nduca, 2014/02/20 07:04:54]

you need a private virtual destructor, even if its got an empty implemetnation.
private so you cant delete it except from the implementation

[etienneb, 2014/02/20 19:08:03]

Done.

+  // Request the ETW trace controller to activate the kernel tracing.
+  // returns true on success, false if the kernel tracing isn't activated.
+  bool StartKernelSessionTracing();
+
+  // Request the ETW trace controller to deactivate the kernel tracing.
+  // returns true on success, false if an error occurred.
+  bool StopKernelSessionTracing();
+
+  // Send a request to the ETWConsumerThread to consume the kernel events.
+  void RequestStartTraceConsuming();

[nduca, 2014/02/20 07:04:54]

my request to keep this internal to the file remains. it may make sense to you
but its hard to understand as a user of the code. you should have basically

    bool Start() --- if it doesn't start, then the systracE_state accordingly

    BeginToStop(callback&) --- stops the tracing, waits for it to drain, kills
the thread, stops the callback

Thats all there should be.

[etienneb, 2014/02/20 19:08:03]

Done.

+
+  // Send a request to the ETWConsumerThread to stop consuming the kernel
+  // events.
+  // @param callback the callback to call with the consuming result.
+  void RequestStopTraceConsuming(const OutputCallback& callback);
+
+  // Retrieve the ETW consumer instance.

[nduca, 2014/02/20 07:04:54]

forgive me if i asked this once but can't we use the standard singleton pattern?
see base/debug/trace_event_impl.h's TraceLog for instance?

[etienneb, 2014/02/20 19:08:03]

Done.

+  static EtwSystemEventConsumer* Get();
+
+  // Static override of EtwTraceConsumerBase::ProcessEvent.
+  // @param event the raw ETW event to process.
+  static void ProcessEvent(EVENT_TRACE* event);
+
+ private:
+  void AppendEventToBuffer(EVENT_TRACE* event);
+
+  void TraceAndConsumeOnThread();
+  void StopAndFlushOnThread(const OutputCallback& callback);
+
+  scoped_ptr<base::ListValue> events_;
+  base::Thread thread_;
+  TRACEHANDLE session_handle_;
+  base::win::EtwTraceProperties properties_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_TRACING_TRACING_CONSUMER_WIN_H_