Fix flakey test by making sure WebUI dialog is shut down before test completion.

chrome/browser/printing/print_dialog_cloud_uitest.cc

Index: chrome/browser/printing/print_dialog_cloud_uitest.cc
diff --git a/chrome/browser/printing/print_dialog_cloud_uitest.cc b/chrome/browser/printing/print_dialog_cloud_uitest.cc
index a1285e530f6115da051374212d3020dfb50f26af..2354dc41fe51f088dc42b0fab9bac6435f95d52a 100644
--- a/chrome/browser/printing/print_dialog_cloud_uitest.cc
+++ b/chrome/browser/printing/print_dialog_cloud_uitest.cc
@@ -236,6 +236,13 @@ IN_PROC_BROWSER_TEST_F(PrintDialogCloudTest, HandlersRegistered) {
   ui_test_utils::RunMessageLoop();
 
   ASSERT_TRUE(TestController::GetInstance()->result());
+
+  // Close the dialog before finishing the test.
+  ui_test_utils::WindowedNotificationObserver signal(
+      content::NOTIFICATION_TAB_CLOSED, NotificationService::AllSources());
+  EXPECT_TRUE(ui_test_utils::SendKeyPressSync(browser(), ui::VKEY_ESCAPE,
+                                              false, false, false, false));
+  signal.Wait();
 }
 
 #if defined(OS_CHROMEOS)