Defer Posting StoreMetricsClientInfo During PreCreateThreads

chrome/browser/metrics/chrome_metrics_services_manager_client.cc

 // 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.
 
 #include "chrome/browser/metrics/chrome_metrics_services_manager_client.h"
 
 #include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 41 matching lines @@
 
 // Metrics reporting feature. This feature, along with user consent, controls if
 // recording and reporting are enabled. If the feature is enabled, but no
 // consent is given, then there will be no recording or reporting.
 const base::Feature kMetricsReportingFeature{"MetricsReporting",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Posts |GoogleUpdateSettings::StoreMetricsClientInfo| on blocking pool thread
 // because it needs access to IO and cannot work from UI thread.
 void PostStoreMetricsClientInfo(const metrics::ClientInfo& client_info) {
-  content::BrowserThread::GetBlockingPool()->PostTask(
-      FROM_HERE,
-      base::Bind(&GoogleUpdateSettings::StoreMetricsClientInfo, client_info));
+  // The delayed post task allows this function to get called before the
+  // blocking pool is ready to go.

[gab, 2016/12/13 15:58:39]

(this sentence is backwards?)

// Posting the task from the main message loop ensures the blocking pool is
initialized (which it isn't always at this point).

[robliao, 2016/12/13 18:19:38]

Clarified to
// The message loop processes messages after the blocking pool is initialized.
// Posting a task to the message loop to post a task to the blocking pool
// ensures that the blocking pool is ready to accept tasks at that time.

+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI, FROM_HERE,
+      base::Bind(
+          [](const metrics::ClientInfo& client_info) {
+            content::BrowserThread::PostBlockingPoolTask(
+                FROM_HERE,
+                base::Bind(&GoogleUpdateSettings::StoreMetricsClientInfo,
+                           client_info));
+          },
+          client_info));
 }
 
 // Appends a group to the sampling controlling |trial|. The group will be
 // associated with a variation param for reporting sampling |rate| in per mille.
 void AppendSamplingTrialGroup(const std::string& group_name,
                               int rate,
                               base::FieldTrial* trial) {
   std::map<std::string, std::string> params = {
       {kRateParamName, base::IntToString(rate)}};
   variations::AssociateVariationParams(trial->trial_name(), group_name, params);
@@ skipping 203 matching lines @@
 ChromeMetricsServicesManagerClient::GetMetricsStateManager() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!metrics_state_manager_) {
     metrics_state_manager_ = metrics::MetricsStateManager::Create(
         local_state_, enabled_state_provider_.get(),
         base::Bind(&PostStoreMetricsClientInfo),
         base::Bind(&GoogleUpdateSettings::LoadMetricsClientInfo));
   }
   return metrics_state_manager_.get();
 }