Let IndexedDBContextImpl create its own task runner

chrome/browser/browsing_data/browsing_data_indexed_db_helper_unittest.cc

Index: chrome/browser/browsing_data/browsing_data_indexed_db_helper_unittest.cc
diff --git a/chrome/browser/browsing_data/browsing_data_indexed_db_helper_unittest.cc b/chrome/browser/browsing_data/browsing_data_indexed_db_helper_unittest.cc
index d2bb71376b3f90d2262f18d8644a7f54b8d8a4a1..af65c46814034da685a8afaf4473f06ea2b08172 100644
--- a/chrome/browser/browsing_data/browsing_data_indexed_db_helper_unittest.cc
+++ b/chrome/browser/browsing_data/browsing_data_indexed_db_helper_unittest.cc
@@ -16,11 +16,6 @@ namespace {
 
 class CannedBrowsingDataIndexedDBHelperTest : public testing::Test {
  public:
-  void SetUp() override {
-    IndexedDBContext()->SetTaskRunnerForTesting(
-        base::ThreadTaskRunnerHandle::Get().get());
-  }
-
   content::IndexedDBContext* IndexedDBContext() {
     return content::BrowserContext::GetDefaultStoragePartition(&profile_)->
         GetIndexedDBContext();