[Background Fetch] Cleanup/fix thread safety

content/browser/background_fetch/background_fetch_service_unittest.cc

Index: content/browser/background_fetch/background_fetch_service_unittest.cc
diff --git a/content/browser/background_fetch/background_fetch_service_unittest.cc b/content/browser/background_fetch/background_fetch_service_unittest.cc
index 46b495da2571d48a36e41af44400be2cc7d9d564..4f405523182447f70c0cb4402c9a665650df1352 100644
--- a/content/browser/background_fetch/background_fetch_service_unittest.cc
+++ b/content/browser/background_fetch/background_fetch_service_unittest.cc
@@ -121,12 +121,14 @@ class BackgroundFetchServiceTest : public BackgroundFetchTestBase {
   void SetUp() override {
     BackgroundFetchTestBase::SetUp();
 
+    // StoragePartition creates its own BackgroundFetchContext, but this test
+    // doesn't use that since it has the wrong ServiceWorkerContextWrapper; this
+    // test just uses the StoragePartition to get a URLRequestContext.
     StoragePartitionImpl* storage_partition =
         static_cast<StoragePartitionImpl*>(
             BrowserContext::GetDefaultStoragePartition(browser_context()));
-
     context_ = new BackgroundFetchContext(
-        browser_context(), storage_partition,
+        browser_context(),
         make_scoped_refptr(embedded_worker_test_helper()->context_wrapper()));
     context_->InitializeOnIOThread(
         make_scoped_refptr(storage_partition->GetURLRequestContext()));
@@ -140,7 +142,6 @@ class BackgroundFetchServiceTest : public BackgroundFetchTestBase {
 
     service_.reset();
 
-    context_->Shutdown();
     context_ = nullptr;
 
     // Give pending shutdown operations a chance to finish.