Test FilesApp QuickView [open] attribute

FileApp QuickView has an [open] attribute, present when it (QuickView)
is open, and removed when it's not open. Verify the attribute appears,
and disappears, for all quick_view.js tests.

No change in behavior, no new tests.

Bug: 891150
Change-Id: If90ae81cd60cd350497dece3896173f432571ccc
Reviewed-on: https://chromium-review.googlesource.com/1256465Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595732}

ui/file_manager/integration_tests/file_manager/quick_view.js

@@ -37,7 +37,7 @@ function openQuickViewSteps(appId, name) {
     function(result) {
       chrome.test.assertTrue(!!result, 'fakeKeyDown failed');
       repeatUntil(function() {
-        const elements = ['#quick-view', '#dialog'];
+        const elements = ['#quick-view', '#dialog[open]'];
         return remoteCall
             .callRemoteTestUtil(
                 'deepQueryAllElements', appId, [elements, ['display']])
@@ -75,7 +75,7 @@ function closeQuickViewSteps(appId) {
     function(result) {
       chrome.test.assertTrue(!!result, 'fakeMouseClick failed');
       repeatUntil(function() {
-        const elements = ['#quick-view', '#dialog'];
+        const elements = ['#quick-view', '#dialog:not([open])'];
         return remoteCall
             .callRemoteTestUtil(
                 'deepQueryAllElements', appId, [elements, ['display']])