Reset sync right away if devices size <= 1

[darkdh]

fix brave/brave-browser#2533
fix brave/brave-browser#2552
fix brave/brave-browser#2728
fix brave/brave-browser#2737

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

Setup sync without second device

1. Create new sync chain on device A
2. Remember the sync code
3. Close all dialog
4. Create new sync chain on device A
5. Sync code should be different than step 2
6. Should able to see QR code

Setup sync with second device and delete second device

1. Create new sync chain on device A
2. Remember the sync code
3. Connect device B
4. Wait for device list synced on both devices
5. Delete device B from device A
6. Wait for both devices showing initial sync page
7. Create new sync chain on device A
8. Sync code should be different than step 2
9. Create new sync chain on device B
10. Sync code should be different than step 2

Setup sync with second device and self deleted

1. Create new sync chain on device A
2. Remember the sync code
3. Connect device B
4. Wait for device list synced on both devices
5. Delete/reset device A on device A
6. Wait for both devices showing initial sync page
7. Create new sync chain on device A
8. Sync code should be different than step 2
9. Create new sync chain on device B
10. Sync code should be different than step 2

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[AlexeyBarabash]

Also fixes brave/brave-browser#2737 .

[AlexeyBarabash]

looks good

[darkdh]

master 4c5d9d8
0.60.x e956513

[bbondy]

0.59.x: a81ec8b

[kjozwiak]

@bbondy looks like this landed in 0.59.x correct? The associated issues mentioned above are all in the 0.60.x milestone. Moving these into https://github.com/brave/brave-browser/milestone/15 (0.59.x).

[srirambv]

Verification passed on 0.59.34. Verified test plan works fine