Sync input fields should have focus when clicked

[srirambv]

• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  Sync input fields should have focus when enabled

• Platform (Win7, 8, 10? macOS? Linux distro?):
  All

• Brave Version (revision SHA):
  Brave 0.15.312
  rev cc653ff
  Muon 3.0.202

• Steps to reproduce:

  1. Open about:preferences#sync
  2. Click on I am new to Sync or I have an existing Sync code
  3. Focus is not on the input field, user has to click and then start typing

• Actual result:
  Sync input fields should have focus when clicked

• Expected result:
  Behavior should be similar to autofill modal. Focus should be set on the first input field when clicked

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  Yes

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:

• Any related issues:
  Autofill should automatically move cursor to first entry when adding a new record #8280
  cc: @kumarrishav

[lzmartinico]

I will take this bug as my first contribution to Brave!

[luixxiul]

@lzmartinico thanks! If you have finished the work on your PR, would you mind tagging a reviewer, following the instruction available here? https://github.com/brave/browser-laptop/wiki/Pull-request-process

[lzmartinico]

@luixxiul Thanks for tagging some reviewers yourself, I don't think I had the right permission

[luixxiul]

I don't think I had the right permission

CC @diracdeltas for investigation.