Fix ArcAppModelBuilderTest

chrome/browser/ui/app_list/app_list_test_util.cc

Index: chrome/browser/ui/app_list/app_list_test_util.cc
diff --git a/chrome/browser/ui/app_list/app_list_test_util.cc b/chrome/browser/ui/app_list/app_list_test_util.cc
index ba33a982301d1eda14bbc3d63de0ac3b435ae202..b9f41b9698cd7657b3a30712edd50c49ad94f248 100644
--- a/chrome/browser/ui/app_list/app_list_test_util.cc
+++ b/chrome/browser/ui/app_list/app_list_test_util.cc
@@ -37,6 +37,14 @@ void AppListTestBase::SetUp() {
   InitializeInstalledExtensionService(pref_path, source_install_dir);
   service_->Init();
 
+  // ExtensionService needs a real I/O thread.
+  service_->SetFileTaskRunnerForTesting(
+      content::BrowserThread::GetBlockingPool()
+          ->GetSequencedTaskRunnerWithShutdownBehavior(
+              content::BrowserThread::GetBlockingPool()->GetNamedSequenceToken(
+                  "ext_install-"),
+              base::SequencedWorkerPool::SKIP_ON_SHUTDOWN));
+
   // There should be 4 extensions in the test profile.
   ASSERT_EQ(4U, registry()->enabled_extensions().size());
 }