Do not register synthetic field trial before initializing TaskScheduler.

chrome/browser/chrome_browser_main.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 "chrome/browser/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 860 matching lines @@
                   variations_service->CreateTrialsFromSeed(feature_list.get());
 
   browser_field_trials_.SetupFeatureControllingFieldTrials(has_seed,
                                                            feature_list.get());
 
   base::FeatureList::SetInstance(std::move(feature_list));
 
   // This must be called after |local_state_| is initialized.
   browser_field_trials_.SetupFieldTrials();
 
-  // Enable Navigation Tracing only if a trace upload url is specified.
-  if (command_line->HasSwitch(switches::kEnableNavigationTracing) &&
-      command_line->HasSwitch(switches::kTraceUploadURL)) {
-    tracing::SetupNavigationTracing();
-  }
-
   // Initialize FieldTrialSynchronizer system. This is a singleton and is used
   // for posting tasks via base::Bind. Its deleted when it goes out of scope.
   // Even though base::Bind does AddRef and Release, the object will not be
   // deleted after the Task is executed.
   field_trial_synchronizer_ = new FieldTrialSynchronizer();
-
-  // Register a synthetic field trial for the sampling profiler configuration
-  // that was already chosen.
-  sampling_profiler_config_.RegisterSyntheticFieldTrial();
-
-#if defined(OS_WIN) || defined(OS_MACOSX) || \
-    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
-  metrics::DesktopSessionDurationTracker::Initialize();
-#endif
-
-#if defined(OS_WIN)
-  // Cleanup the PreRead field trial registry key.
-  // TODO(fdoray): Remove this when M56 hits stable.
-  const base::string16 pre_read_field_trial_registry_path =
-      BrowserDistribution::GetDistribution()->GetRegistryPath() +
-      L"\\PreReadFieldTrial";
-  base::win::RegKey(HKEY_CURRENT_USER,
-                    pre_read_field_trial_registry_path.c_str(), KEY_SET_VALUE)
-      .DeleteKey(L"");
-#endif  // defined(OS_WIN)
 }
 
 void ChromeBrowserMainParts::SetupMetrics() {
   TRACE_EVENT0("startup", "ChromeBrowserMainParts::SetupMetrics");
   metrics::MetricsService* metrics = browser_process_->metrics_service();
   metrics->AddSyntheticTrialObserver(
       variations::VariationsHttpHeaderProvider::GetInstance());
   // Now that field trials have been created, initializes metrics recording.
   metrics->InitializeMetricsRecordingState();
 
   const version_info::Channel channel = chrome::GetChannel();
 
   // Enable profiler instrumentation depending on the channel.
   switch (channel) {
     case version_info::Channel::UNKNOWN:
     case version_info::Channel::CANARY:
       tracked_objects::ScopedTracker::Enable();
       break;
 
     case version_info::Channel::DEV:
     case version_info::Channel::BETA:
     case version_info::Channel::STABLE:
       // Don't enable instrumentation.
       break;
   }
+
+  // Enable Navigation Tracing only if a trace upload url is specified.
+  const base::CommandLine* command_line =
+      base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kEnableNavigationTracing) &&
+      command_line->HasSwitch(switches::kTraceUploadURL)) {
+    tracing::SetupNavigationTracing();

[robliao, 2016/09/30 01:10:09]

This section seems like it could go outside of SetupMetrics. Is this triggering
issues?

[fdoray, 2016/09/30 12:36:42]

No longer changing this section in this CL.

+  }
+
+#if defined(OS_WIN) || defined(OS_MACOSX) || \
+    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+  metrics::DesktopSessionDurationTracker::Initialize();
+#endif
 }
 
 void ChromeBrowserMainParts::StartMetricsRecording() {
   TRACE_EVENT0("startup", "ChromeBrowserMainParts::StartMetricsRecording");
 
   g_browser_process->metrics_service()->CheckForClonedInstall(
       BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE));
 
+  // Register a synthetic field trial for the sampling profiler configuration
+  // that was already chosen. This must be done before the line below creates
+  // the first MetricsLog.
+  sampling_profiler_config_.RegisterSyntheticFieldTrial();
+
   g_browser_process->GetMetricsServicesManager()->UpdateUploadPermissions(true);
 }
 
 void ChromeBrowserMainParts::RecordBrowserStartupTime() {
   // Don't record any metrics if UI was displayed before this point e.g.
   // warning dialogs.
   if (startup_metric_utils::WasNonBrowserUIDisplayed())
     return;
 
   bool is_first_run = false;
@@ skipping 569 matching lines @@
 #if !defined(OS_ANDROID)
   if (base::FeatureList::IsEnabled(features::kWebUsb)) {
     web_usb_detector_.reset(new WebUsbDetector());
     BrowserThread::PostAfterStartupTask(
         FROM_HERE, BrowserThread::GetTaskRunnerForThread(BrowserThread::UI),
         base::Bind(&WebUsbDetector::Initialize,
                    base::Unretained(web_usb_detector_.get())));
   }
 #endif
 
+#if defined(OS_WIN)
+  // Cleanup the PreRead field trial registry key.
+  // TODO(fdoray): Remove this when M56 hits stable.
+  const base::string16 pre_read_field_trial_registry_path =

[robliao, 2016/09/30 01:10:09]

Can this be done in a separate CL?

[fdoray, 2016/09/30 12:36:41]

Done. Made the CL smaller.

+      BrowserDistribution::GetDistribution()->GetRegistryPath() +
+      L"\\PreReadFieldTrial";
+  base::win::RegKey(HKEY_CURRENT_USER,
+                    pre_read_field_trial_registry_path.c_str(), KEY_SET_VALUE)
+      .DeleteKey(L"");
+#endif  // defined(OS_WIN)
+
   // At this point, StartupBrowserCreator::Start has run creating initial
   // browser windows and tabs, but no progress has been made in loading
   // content as the main message loop hasn't started processing tasks yet.
   // We setup to observe to the initial page load here to defer running
   // task posted via PostAfterStartupTask until its complete.
   AfterStartupTaskUtils::StartMonitoringStartup();
 }
 
 int ChromeBrowserMainParts::PreMainMessageLoopRunImpl() {
   TRACE_EVENT0("startup", "ChromeBrowserMainParts::PreMainMessageLoopRunImpl");
@@ skipping 674 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }