Use TaskScheduler instead of blocking pool in chrome_metrics_services_manager_client.cc.

The blocking pool is being deprecated in favor of TaskScheduler.

BUG=667892
R=rkaplow@chromium.org

Review-Url: https://codereview.chromium.org/2769803002
Cr-Commit-Position: refs/heads/master@{#467681}

chrome/browser/metrics/chrome_metrics_services_manager_client.cc

@@ -9,6 +9,7 @@
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/task_scheduler/post_task.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/metrics/chrome_metrics_service_accessor.h"
 #include "chrome/browser/metrics/chrome_metrics_service_client.h"
@@ -62,19 +63,13 @@ const base::Feature kMetricsReportingFeature{"MetricsReporting",
 // 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) {
-  // 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::BindOnce(
-          [](const metrics::ClientInfo& client_info) {
-            content::BrowserThread::PostBlockingPoolTask(
-                FROM_HERE,
-                base::BindOnce(&GoogleUpdateSettings::StoreMetricsClientInfo,
-                               client_info));
-          },
-          client_info));
+  base::PostTaskWithTraits(
+      FROM_HERE,
+      base::TaskTraits()
+          .WithPriority(base::TaskPriority::BACKGROUND)
+          .MayBlock(),
+      base::BindOnce(&GoogleUpdateSettings::StoreMetricsClientInfo,
+                     client_info));
 }
 
 // Appends a group to the sampling controlling |trial|. The group will be