[Cleanup] Migrate the DriveMetricsProvider to use the Task Scheduler.

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm

Index: ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm
diff --git a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm
index 708a235d0e8876813af8d0f0af7d387a02310cef..bb9a83050f30d28253abfca0691f045e7287eea1 100644
--- a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm
+++ b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm
@@ -223,9 +223,7 @@ void IOSChromeMetricsServiceClient::Initialize() {
 
   {
     auto drive_metrics_provider =
-        base::MakeUnique<metrics::DriveMetricsProvider>(
-            web::WebThread::GetTaskRunnerForThread(web::WebThread::FILE),
-            ios::FILE_LOCAL_STATE);
+        base::MakeUnique<metrics::DriveMetricsProvider>(ios::FILE_LOCAL_STATE);
     drive_metrics_provider_ = drive_metrics_provider.get();
     metrics_service_->RegisterMetricsProvider(
         std::move(drive_metrics_provider));