Revert "Disable feedback panels by default"

This reverts commit e919a379.

Reason for revert: Flag was disabled for landing on 77 branch, so reverting this to enable it again for 78.

Original change's description:
> Disable feedback panels by default
> 
> Bug: 999653
> Change-Id: I3c2a65fc04817a1ced86ecbd5157877a6ac07244
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1778883
> Commit-Queue: Alex Danilo <adanilo@chromium.org>
> Commit-Queue: Austin Tankiang <austinct@chromium.org>
> Auto-Submit: Alex Danilo <adanilo@chromium.org>
> Reviewed-by: Austin Tankiang <austinct@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#692200}

TBR=adanilo@chromium.org,austinct@chromium.org

Change-Id: I7860daf73b48f18f7c05fc9155f16f328c09d124
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 999653
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1779463Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692263}

chromeos/constants/chromeos_features.cc

@@ -83,7 +83,7 @@ const base::Feature kDriveFsMirroring{"DriveFsMirroring",
 
 // If enabled shows the visual signals feedback panel.
 const base::Feature kEnableFileManagerFeedbackPanel{
-    "EnableFeedbackPanel", base::FEATURE_DISABLED_BY_DEFAULT};
+    "EnableFeedbackPanel", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables the enhanced external media formatting dialog in the file manager,
 // with support for labelling and also NTFS/exFAT filesystems.

ui/file_manager/integration_tests/file_manager/transfer.js

@@ -600,12 +600,13 @@ testcase.transferDeletedFile = async () => {
   chrome.test.assertTrue(
       await remoteCall.callRemoteTestUtil('execCommand', appId, ['paste']));
 
-  // Wait for the progress center to display.
-  await remoteCall.waitForElement(appId, '#progress-center:not([hidden])');
-
-  // Check that the error appears in the progress center.
-  const element =
-      await remoteCall.waitForElement(appId, '.progress-frame label');
+  // Check that the error appears in the feedback panel.
+  const element = await remoteCall.waitForElement(
+      appId, ['#progress-panel', 'xf-panel-item']);
   chrome.test.assertEq(
-      `Whoops, ${entry.nameText} no longer exists.`, element.text);
+      `Whoops, ${entry.nameText} no longer exists.`,
+      element.attributes['primary-text']);
+
+  // Check that only one line of text is shown.
+  chrome.test.assertFalse(!!element.attributes['secondary-text']);
 };