The MigrationWizard can be embedded in a dialog (either a stand-alone dialog window, or a TabDialogBox), or on its own in a privileged about: page.

In the former case, we want to make it possible to have "Cancel" buttons that will close the dialog.

This bug is for adding a "dialog-mode" attribute to the MigrationWizard that can be used to determine whether or not to show dialog-closing "Cancel" buttons, and then to respond appropriately within the migration-dialog.html document.

Depends on D165090

Backed out for causing failures on browser_dialog_cancel_close.js

• backout: https://hg.mozilla.org/integration/autoland/rev/4c3a6ff0488d28edc0d080b93682c156a24526d6
• push: https://treeherder.mozilla.org/jobs?repo=autoland&revision=57167994f0267ab208e6920d906fdf89328f34f9
• tier 1 failures: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&selectedTaskRun=GuaxgEN3SXyRGxJbpiOlQA.0&revision=97fc9f3f9d3900213938afb48980e0a1fec9f4ee&searchStr=browser-chrome
• failure log: https://treeherder.mozilla.org/logviewer?job_id=402369775&repo=autoland&lineNumber=5210

[task 2023-01-14T01:44:39.879Z] 01:44:39     INFO - TEST-PASS | browser/components/migration/tests/browser/browser_dialog_cancel_close.js | Dialog manager has a dialog. - 1 == 1 - 
[task 2023-01-14T01:44:39.881Z] 01:44:39     INFO - Waiting for dialogs to open.
[task 2023-01-14T01:44:39.881Z] 01:44:39     INFO - Console message: [JavaScript Warning: "Unknown category for SetEventRecordingEnabled: page_load"]
[task 2023-01-14T01:44:39.883Z] 01:44:39     INFO - Console message: [JavaScript Warning: "Unknown category for SetEventRecordingEnabled: page_load"]
[task 2023-01-14T01:44:39.883Z] 01:44:39     INFO - Buffered messages logged at 01:43:55
[task 2023-01-14T01:44:39.887Z] 01:44:39     INFO - Console message: [JavaScript Error: "Error: Can't find profile directory." {file: "resource://gre/modules/XULStore.jsm" line: 58}]
[task 2023-01-14T01:44:39.888Z] 01:44:39     INFO - load@resource://gre/modules/XULStore.jsm:58:15
[task 2023-01-14T01:44:39.890Z] 01:44:39     INFO - XULStore@resource://gre/modules/XULStore.jsm:17:10
[task 2023-01-14T01:44:39.890Z] 01:44:39     INFO - 
[task 2023-01-14T01:44:39.891Z] 01:44:39     INFO - Buffered messages finished
[task 2023-01-14T01:44:39.892Z] 01:44:39     INFO - TEST-UNEXPECTED-FAIL | browser/components/migration/tests/browser/browser_dialog_cancel_close.js | Test timed out - 
[task 2023-01-14T01:44:39.894Z] 01:44:39     INFO - Not taking screenshot here: see the one that was previously logged
[task 2023-01-14T01:44:39.895Z] 01:44:39     INFO - TEST-UNEXPECTED-FAIL | browser/components/migration/tests/browser/browser_dialog_cancel_close.js | Uncaught exception received from previously timed out test - MigrationWizard:Ready listener not removed before the end of test
[task 2023-01-14T01:44:39.896Z] 01:44:39     INFO - Entering test bound test_cancel_close
[task 2023-01-14T01:44:39.896Z] 01:44:39     INFO - TEST-PASS | browser/components/migration/tests/browser/browser_dialog_cancel_close.js | Window was closed. - true == true - 

https://hg.mozilla.org/mozilla-central/rev/1987a6cc967c