Fixed extensions import

[spylogsster]

Resolves brave/brave-browser#27487

Extensions import was broken in new import UI, fixed it.

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run lint, npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

• steps from issue

[simonhong]

Could we delete this define https://github.com/brave/brave-core/blob/master/chromium_src/chrome/browser/ui/webui/settings/import_data_handler.cc#L9?
As we re-implement StartImport() at BraveImportDataHandler?

[simonhong]

++

[spylogsster]

Could we delete this define https://github.com/brave/brave-core/blob/master/chromium_src/chrome/browser/ui/webui/settings/import_data_handler.cc#L9? As we re-implement StartImport() at BraveImportDataHandler?

follow up brave/brave-browser#27515

[kjozwiak]

Verification PASSED on Win 11 x64 using the following build(s):

Brave | 1.48.97 Chromium: 109.0.5414.46 (Official Build) nightly (64-bit)
-- | --
Revision | 6e36b77363ef3febbe792af680fa1367993ddcf0-refs/branch-heads/5414@{#709}
OS | Windows 11 Version 22H2 (Build 22621.963)

Using the STR/Cases outlined via brave/brave-browser#27487 (comment), ensured that extensions from Chromium based browsers can be imported into Brave without any issues as per the following:

• ensured that extensions installed by users via other browsers are being imported via brave://welcome
• ensured that extensions installed by users via other browsers are being imported via brave://settings/importData
  • ensured that extensions are being imported if it's the only option selected
  • ensured that extensions are being imported when all the options are selected
• ensured that cookies are not being imported (for example, passwords)
• ensured that all the extensions are being listed under brave://extensions

Importing from Chrome

Example	Example	Example	Example	Example

Importing from Edge

Example	Example	Example	Example	Example