[ETW Export] Add polling for ETW keyword.

content/browser/browser_main_loop.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/browser_main_loop.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/memory/memory_pressure_monitor.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/pending_task.h"
 #include "base/power_monitor/power_monitor.h"
 #include "base/power_monitor/power_monitor_device_source.h"
 #include "base/process/process_metrics.h"
 #include "base/profiler/scoped_profile.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/system_monitor/system_monitor.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/timer/hi_res_timer_manager.h"
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/trace_event.h"
+#include "base/trace_event/trace_event_etw_export_win.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/device_sensors/device_inertial_sensor_service.h"
 #include "content/browser/dom_storage/dom_storage_area.h"
 #include "content/browser/download/save_file_manager.h"
 #include "content/browser/gamepad/gamepad_service.h"
 #include "content/browser/gpu/browser_gpu_channel_host_factory.h"
 #include "content/browser/gpu/browser_gpu_memory_buffer_manager.h"
 #include "content/browser/gpu/compositor_util.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
 #include "content/browser/gpu/gpu_process_host.h"
@@ skipping 651 matching lines @@
     GpuDataManagerImpl::GetInstance()->Initialize();
   }
 
 #if !defined(OS_IOS) && (!defined(GOOGLE_CHROME_BUILD) || defined(OS_ANDROID))
   // Single-process is an unsupported and not fully tested mode, so
   // don't enable it for official Chrome builds (except on Android).
   if (parsed_command_line_.HasSwitch(switches::kSingleProcess))
     RenderProcessHost::SetRunRendererInProcess(true);
 #endif
 
+#if defined(OS_WIN)
+  // Starts a timer to poll the ETW keyword (flags), that checks if a consumer
+  // is listening and if the categories have changed.
+  base::trace_event::TraceEventETWExport::StartKeywordUpdateTimer();

[brucedawson, 2015/06/26 22:24:24]

Does this get called in just the browser or in all processes?

If in just the browser then the other processes will never emit events.
If in all processes then we can end up with arbitrarily many wakeups per second.

Ideal implementation would do the timer-based checking in just the browser
process and then send an IPC message to the other processes when there is a
change. I'm not sure if that is overkill or ideal.

+#endif
+
   return result_code_;
 }
 
 void BrowserMainLoop::CreateStartupTasks() {
   TRACE_EVENT0("startup", "BrowserMainLoop::CreateStartupTasks");
   TRACK_SCOPED_REGION("Startup", "BrowserMainLoop::CreateStartupTasks");
 
   // First time through, we really want to create all the tasks
   if (!startup_task_runner_.get()) {
 #if defined(OS_ANDROID)
@@ skipping 639 matching lines @@
   DCHECK(is_tracing_startup_);
 
   is_tracing_startup_ = false;
   TracingController::GetInstance()->DisableRecording(
       TracingController::CreateFileSink(
           startup_trace_file_,
           base::Bind(OnStoppedStartupTracing, startup_trace_file_)));
 }
 
 }  // namespace content