Fix transferInfoIsRemembered test

Changes test to use the deserialised attribute values for comparing the
attributes set on feedback panels for copy operations.

Bug: 988137
Tests: browser_tests --gtest_filter="*FilesAppBrowserTest.Test/transferInfoIsRemembered"
Change-Id: I5086a1feeeba9c06331ddc711ccc298e0f6574ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906862Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714177}

ui/file_manager/integration_tests/file_manager/transfer.js

@@ -639,8 +639,8 @@ testcase.transferInfoIsRemembered = async () => {
   // The feedback panel should appear: record the feedback panel text.
   let panel = await remoteCall.waitForElement(
       appId, ['#progress-panel', 'xf-panel-item']);
-  const primaryText = panel.primaryText;
-  const secondaryText = panel.secondaryText;
+  const primaryText = panel.attributes['primary-text'];
+  const secondaryText = panel.attributes['secondary-text'];
 
   // Close the Files app window.
   await remoteCall.closeWindowAndWait(appId);
@@ -651,6 +651,6 @@ testcase.transferInfoIsRemembered = async () => {
   // Check the feedback panel text is remembered.
   panel = await remoteCall.waitForElement(
       appId, ['#progress-panel', 'xf-panel-item']);
-  chrome.test.assertEq(primaryText, panel.primaryText);
-  chrome.test.assertEq(secondaryText, panel.secondaryText);
+  chrome.test.assertEq(primaryText, panel.attributes['primary-text']);
+  chrome.test.assertEq(secondaryText, panel.attributes['secondary-text']);
 };