Add in-browser prompt to import Google Passwords

[CDRussell]

Task/Issue URL: https://app.asana.com/1/137249556945/project/608920331025315/task/1210270953487596?focus=true

Description

Adds ability to show a prompt offering to import passwords from Google at a time when it's most useful to the user: when they've hit a login form and they haven't imported before.

Steps to test this PR

• Fresh install from this branch
• Visit https://fill.dev/form/login-simple
• Tap on username field; verify you see the dialog letting you import Google passwords

Soft-Dismiss scenarios

• Tap on the ✖️ button to dismiss it [dismiss count == 1]; verify it dismisses
• Tap on password field; verify it doesn't show again (it shouldn't show more than once on a page load)
• Refresh the page and tap on username field again; verify the dialog shows again
• Tap the back button [dismiss count == 2]; verify the dialog dismisses
• Tap on password field; verify it doesn't show again (it shouldn't show more than once on a page load)
• Refresh the page and tap on username field again; verify the dialog shows again
• Tap outside the dialog [dismiss count == 3]; verify the dialog dismisses
• Refresh the page and tap on username field again; verify the dialog shows again
• Tap the ✖️ button again [dismiss count == 4]
• Refresh the page and tap on username field again; verify the dialog shows again
• Tap the ✖️ button again [dismiss count == 5]
• Refresh the page and tap on username field again; verify the dialog shows again
• Tap the ✖️ button again [dismiss count == 6]
• Refresh the page and tap on username field again; verify the dialog does not show again

Hard-Dismiss scenario

• Fresh install from this branch (or use the autofill dev setting called Previous Google Imports to clear previous knowledge of the import dialogs)
• Visit https://fill.dev/form/login-simple
• Tap on username field; verify you see the dialog letting you import Google passwords
• Tap on Set Up Later in Settings button; verify the dialog dismisses
• Refresh the page and tap on username field again; verify the dialog does not show again

Site already has credentials

• Fresh install from this branch (or use the autofill dev setting called Previous Google Imports to clear previous knowledge of the import dialogs)
• Manually add a login credential for fill.dev in the autofill management screen
• Visit https://fill.dev/form/login-simple
• Decline to autofill
• Tap on username field; verify you are not prompted to import passwords

Completing import scenario

• Add a password for fill.dev to your Google Passwords; instructions for doing so can be found here
• Fresh install from this branch
• Visit https://fill.dev/form/login-simple
• Tap on username field; tap Import From Google button and complete the import flow
• Verify you see the import success dialog showing how many credentials were imported
• Dismiss that dialog (doesn't matter how). Verify you are then prompted to autofill with the new credential it just imported and that autofilling works if you agree to do it.

Already imported scenario

• Fresh install from this branch
• Visit Settings -> Passwords & Autofill and tap on Import Passwords from Google button
• Complete the import
• Visit password list and delete any credentials for fill.dev (having a saved password for that site is not the scenario we want to test here)
• Visit https://fill.dev/form/login-simple
• Tap on username field; verify you do not see the dialog letting you import Google passwords

Feature flag disabled scenario

• Fresh install from this branch
• Visit FF inventory and disable canPromoteImportGooglePasswordsInBrowser
• Visit https://fill.dev/form/login-simple
• Tap on username field; verify you do not see the import password dialog

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• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/864955901782631

[CDRussell]

• Add in-browser prompt to import Google Passwords #6290 : 2 dependent PRs (#6368 , #6405 ) 👈 (View in Graphite)
• Force line break in import promo title #6317
• Add dev setting for clearing previous google import flag #6311
• Add source to import flow pixels #6310
• Update promo CTA's copy and remove its icon #6307
• Rename feature flag, to allow for separate flags for each password import promo #6293
• Add icon to the import promo's CTA button #6282
• Change requirement for marking a previous password import as having happened #6281
• Don't show preimport dialog when launching from password import promo #6278
• Show import promo in autofill management #6266
• develop

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[CDRussell]

waiting on stable release; expected imminently

[cmonfortep]

LGTM

just a few comments NITs and one question about capability checks related with reported bug