Bug 1703327, use user agent attribution to pre-select browser in import wizard triggered from new user onboarding Import screen. Scope of this bug is to

a) Update 'Import screen' primary button label to use useragent attribution string e.g. 'Import from Chrome'
b) user agent string should be localized using ftl strings from migration.ftl
c) move await doesAppNeedPin related dynamic changes from AboutWelcomeDefaults.jsm getDefaults call into prepareContentForReact so that dynamic rules are evaluated for both default and experiment data

https://searchfox.org/mozilla-central/source/browser/components/newtab/aboutwelcome/lib/AboutWelcomeDefaults.jsm#441

Relanded patch after fixing test, thanks!

Test Steps:

1. Open about:newtab#devtools after setting pref browser.newtabpage.activity-stream.asrouter.devtoolsEnabled as true
2. Go to Targeting -> Attribution parameter, Empty all prefilled attribution values.
3. Enter User Agent value as 'chrome' and click Force Attribution
4. Open about:welcome and navigate to Import screen. Import button should display 'Import From Chrome'
5. Click of Import From Chrome should open import wizard with 'chrome' browser pre-selected
6. Import button label should be localized for non-en locales

Comment on attachment 9219125 [details]
Bug 1707749 - New user onboarding Import primary button label to use download source

Beta/Release Uplift Approval Request

• User impact if declined: Import button label will stay static and not include browser name from which Firefox was downloaded
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: https://bugzilla.mozilla.org/show_bug.cgi?id=1707749#c7
• List of other uplifts needed: none
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Fixes done as part of proton onboarding MR1 release covered extensively by QA testing
• String changes made/needed: none

Comment on attachment 9219125 [details]
Bug 1707749 - New user onboarding Import primary button label to use download source

Low risk proton uplift, approved for 89 beta 8, thanks.

I have verified this enhancement and I can confirm that the following:

• The "Import from Google Chrome" label is displayed on the primary button from the "Import" screen of the "about:welcome" page if the Firefox browser was downloaded using Chrome
• The "Import from Microsoft Edge" label is displayed if the browser was downloaded using Edge.

Verified using the latest Firefox Nightly (90.0a1 Build ID - 20210504092024) installed on Windows 10 x64, Windows 8.1 x64, and Windows 7 x64.

I have verified this enhancement and I can confirm that the following:

• The "Import from Google Chrome" label is displayed on the primary button from the "Import" screen of the "about:welcome" page if the Firefox browser was downloaded using Chrome
• The "Import from Microsoft Edge" label is displayed if the browser was downloaded using Edge.

Verified using the latest Firefox Beta (89.0b8 Build ID - 20210504185920) installed on Windows 10 x64, Windows 8.1 x64, and Windows 7 x64.