Add option to export tracing events to ETW.

base/trace_event/trace_event_etw_export_win.h

+// 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.
+
+// This file contains the Windows-specific exporting to ETW.
+#ifndef BASE_TRACE_EVENT_TRACE_ETW_EXPORT_H_
+#define BASE_TRACE_EVENT_TRACE_ETW_EXPORT_H_
+
+#include "base/base_export.h"
+#include "base/trace_event/trace_event_impl.h"
+
+// Fwd.
+template <typename Type>
+struct StaticMemorySingletonTraits;
+
+namespace base {
+namespace trace_event {
+
+class BASE_EXPORT TraceEventETWExport {
+ public:
+  ~TraceEventETWExport();
+
+  // Retrieves the singleton.
+  // Note that this may return NULL post-AtExit processing.
+  static TraceEventETWExport* GetInstance();
+
+  // Enables/disables exporting of events to ETW. If disabled,
+  // AddEvent and AddCustomEvent will simply return when called.
+  static void EnableETWExport();
+  static void DisableETWExport();
+
+  static bool isETWExportEnabled() { return GetInstance()->ETWExportEnabled_; }

[Lei Zhang, 2015/04/16 08:11:02]

nit: Is...

+
+  // Exports an event to ETW. This is mainly used in
+  // TraceLog::AddTraceEventWithThreadIdAndTimestamp to export internal events.
+  static void AddEvent(
+      char phase,
+      const unsigned char* category_group_enabled,
+      const char* name,
+      unsigned long long id,
+      int num_args,
+      const char** arg_names,
+      const unsigned char* arg_types,
+      const unsigned long long* arg_values,
+      const scoped_refptr<ConvertableToTraceFormat>* convertable_values);
+
+  // Exports an event to ETW. This should be used when exporting an event only
+  // to ETW. Supports three arguments to be passed to ETW.
+  // TODO(georgesak): Allow different providers.
+  static void AddCustomEvent(const char* name,
+                             char const* phase,

[Lei Zhang, 2015/04/16 08:11:02]

why is this a char const?

+                             const char* arg_name_1,
+                             const char* arg_value_1,
+                             const char* arg_name_2,
+                             const char* arg_value_2,
+                             const char* arg_name_3,
+                             const char* arg_value_3);
+
+  void Resurrect();
+
+ private:
+  bool ETWExportEnabled_;
+  // Ensure only the provider can construct us.
+  friend struct StaticMemorySingletonTraits<TraceEventETWExport>;
+  TraceEventETWExport();
+
+  DISALLOW_COPY_AND_ASSIGN(TraceEventETWExport);
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_TRACE_ETW_EXPORT_H_