[Tracing Clock Sync] Add TracingAgent interface in Chrome

content/browser/tracing/etw_system_event_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_ETW_SYSTEM_EVENT_CONSUMER_WIN_H_
 #define CONTENT_BROWSER_TRACING_ETW_SYSTEM_EVENT_CONSUMER_WIN_H_
 
 #include "base/bind.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/threading/thread.h"
+#include "base/trace_event/tracing_agent.h"
 #include "base/values.h"
 #include "base/win/event_trace_consumer.h"
 #include "base/win/event_trace_controller.h"
 
 namespace base {
 template <typename Type>
 struct DefaultSingletonTraits;
 }
 
 namespace content {
 
-class EtwSystemEventConsumer :
-    public base::win::EtwTraceConsumerBase<EtwSystemEventConsumer> {
+class EtwSystemEventConsumer
+    : public base::win::EtwTraceConsumerBase<EtwSystemEventConsumer>,
+      public base::trace_event::TracingAgent {
  public:
-  typedef base::Callback<void(const scoped_refptr<base::RefCountedString>&)>
-      OutputCallback;
-
-  bool StartSystemTracing();
-  void StopSystemTracing(const OutputCallback& callback);
+  // base::trace_event::TracingAgent implementation.
+  std::string GetTracingAgentName() override;
+  std::string GetTraceEventLabel() override;
+  bool StartAgentTracing(
+      const base::trace_event::TraceConfig& trace_config) override;
+  void StopAgentTracing(const StopAgentTracingCallback& callback) override;
 
   // Retrieve the ETW consumer instance.
   static EtwSystemEventConsumer* GetInstance();
 
  private:
   // This allows constructor and destructor to be private and usable only
   // by the Singleton class.
   friend struct base::DefaultSingletonTraits<EtwSystemEventConsumer>;
 
   // Constructor.
   EtwSystemEventConsumer();
-  virtual ~EtwSystemEventConsumer();
+  ~EtwSystemEventConsumer() override;
 
   void AddSyncEventToBuffer();
   void AppendEventToBuffer(EVENT_TRACE* event);
 
   // Static override of EtwTraceConsumerBase::ProcessEvent.
   // @param event the raw ETW event to process.
   friend class base::win::EtwTraceConsumerBase<EtwSystemEventConsumer>;
   static void ProcessEvent(EVENT_TRACE* event);
 
   // 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.
   // @param callback the callback to call with the consumed events.
   // @returns true on success, false if an error occurred.
   bool StopKernelSessionTracing();
 
   void OnStopSystemTracingDone(
-    const OutputCallback& callback,
+    const StopAgentTracingCallback& callback,
     const scoped_refptr<base::RefCountedString>& result);
 
   void TraceAndConsumeOnThread();
-  void FlushOnThread(const OutputCallback& callback);
+  void FlushOnThread(const StopAgentTracingCallback& callback);
 
   scoped_ptr<base::ListValue> events_;
   base::Thread thread_;
   TRACEHANDLE session_handle_;
   base::win::EtwTraceProperties properties_;
 
   DISALLOW_COPY_AND_ASSIGN(EtwSystemEventConsumer);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_TRACING_ETW_SYSTEM_EVENT_CONSUMER_WIN_H_