Fix event tracing for windows test flakyness....

base/event_trace_provider_win.h

 // Copyright (c) 2009 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.
 //
 // Declaration of a Windows event trace provider class, to allow using
 // Windows Event Tracing for logging transport and control.
 #ifndef BASE_EVENT_TRACE_PROVIDER_WIN_H_
 #define BASE_EVENT_TRACE_PROVIDER_WIN_H_
 #pragma once
 
@@ skipping 108 matching lines @@
   // Do nothing if !ShouldLog(level, 0xFFFFFFFF).
   ULONG Log(const EtwEventClass& event_class, EtwEventType type,
             EtwEventLevel level, const char *message);
   ULONG Log(const EtwEventClass& event_class, EtwEventType type,
             EtwEventLevel level, const wchar_t *message);
 
   // Log the provided event.
   ULONG Log(EVENT_TRACE_HEADER* event);
 
  protected:
-  // These are called after events have been enabled or disabled.
-  // Override them if you want to do processing at the start or
-  // end of collection.
-  // Note: These may be called ETW's thread and they may be racy.
+  // Called after events have been enabled, override in subclasses
+  // to set up state or log at the start of a session.
+  // Note: This function may be called ETW's thread and may be racy,
+  //    bring your own locking if needed.
   virtual void OnEventsEnabled() {}
+
+  // Called just before events are disabled, override in subclasses
+  // to tear down state or log at the end of a session.
+  // Note: This function may be called ETW's thread and may be racy,
+  //    bring your own locking if needed.
   virtual void OnEventsDisabled() {}
 
+  // Called just after events have been disabled, override in subclasses
+  // to tear down state at the end of a session. At this point it's
+  // to late to log anything to the session.
+  // Note: This function may be called ETW's thread and may be racy,
+  //    bring your own locking if needed.
+  virtual void PostEventsDisabled() {}
+
  private:
   ULONG EnableEvents(PVOID buffer);
   ULONG DisableEvents();
   ULONG Callback(WMIDPREQUESTCODE request, PVOID buffer);
   static ULONG WINAPI ControlCallback(WMIDPREQUESTCODE request, PVOID context,
                                       ULONG *reserved, PVOID buffer);
 
   GUID provider_name_;
   TRACEHANDLE registration_handle_;
   TRACEHANDLE session_handle_;
   EtwEventFlags enable_flags_;
   EtwEventLevel enable_level_;
 
   // We don't use this, but on XP we're obliged to pass one in to
   // RegisterTraceGuids. Non-const, because that's how the API needs it.
   static TRACE_GUID_REGISTRATION obligatory_guid_registration_;
 
   DISALLOW_COPY_AND_ASSIGN(EtwTraceProvider);
 };
 
 #endif  // BASE_EVENT_TRACE_PROVIDER_WIN_H_