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

components/metrics/file_metrics_provider_unittest.cc

Index: components/metrics/file_metrics_provider_unittest.cc
diff --git a/components/metrics/file_metrics_provider_unittest.cc b/components/metrics/file_metrics_provider_unittest.cc
index a62ff63273449fc4e514aba4334197b921ace2e4..982e28c06a15236b08e335201981e12e3e4bf932 100644
--- a/components/metrics/file_metrics_provider_unittest.cc
+++ b/components/metrics/file_metrics_provider_unittest.cc
@@ -87,6 +87,7 @@ class FileMetricsProviderTest : public testing::TestWithParam<bool> {
         prefs_(new TestingPrefServiceSimple) {
     EXPECT_TRUE(temp_dir_.CreateUniqueTempDir());
     FileMetricsProvider::RegisterPrefs(prefs_->registry(), kMetricsName);
+    FileMetricsProvider::SetTaskRunnerForTesting(task_runner_);
   }
 
   ~FileMetricsProviderTest() override {
@@ -106,7 +107,7 @@ class FileMetricsProviderTest : public testing::TestWithParam<bool> {
 
   FileMetricsProvider* provider() {
     if (!provider_)
-      provider_.reset(new FileMetricsProvider(task_runner_, prefs()));
+      provider_.reset(new FileMetricsProvider(prefs()));
     return provider_.get();
   }