MD Settings: Defer opening Import Dialog dialog to prevent UI flicker

chrome/test/data/webui/settings/import_data_dialog_test.js

Index: chrome/test/data/webui/settings/import_data_dialog_test.js
diff --git a/chrome/test/data/webui/settings/import_data_dialog_test.js b/chrome/test/data/webui/settings/import_data_dialog_test.js
index 703a00f674e717b3e5c23a1d33babe79c26cc8c4..d053879752555a9328736123f3613e9e617af045 100644
--- a/chrome/test/data/webui/settings/import_data_dialog_test.js
+++ b/chrome/test/data/webui/settings/import_data_dialog_test.js
@@ -95,8 +95,8 @@ suite('ImportDataDialog', function() {
     dialog = document.createElement('settings-import-data-dialog');
     dialog.set('prefs', prefs);
     document.body.appendChild(dialog);
-    assertTrue(dialog.$.dialog.open);
     return browserProxy.whenCalled('initializeImportDialog').then(function() {
+      assertTrue(dialog.$.dialog.open);
       Polymer.dom.flush();
     });
   });