Update favicon from importer

[darkdh]

• 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).
• Ran git rebase -i to squash commits (if needed).

fix #4270

Auditors: @bbondy

Test Plan:

1. Make sure "Favicons" in "about:preferences#general" is on
2. Import bookmarks from other browser or html file
3. There should be favicon for bookmarks

[bbondy]

++