Allow auto-upgrade from browser-laptop via argument

Test plan (run on Win32/Win64/macOS/Linux)

Test: first run

1. Have an install of browser-laptop setup and configured (Release channel) with
   • bookmarks
   • history
   • cookies
   • saved passwords
2. Download/install the brave-core release candidate
3. Delete the brave-core profile (if one was created; sometimes installer will launch Brave after install)
4. Launch brave-core via CLI and make sure to pass --upgrade-from-muon
5. Verify items called out in Step 1 were imported into brave-core

Test: only runs once

After completing steps 1-5 of the first run test:

1. Quit brave-core if it is open
2. Launch brave-core via CLI and make sure to pass --upgrade-from-muon
3. Verify that the auto-import was not repeated. For example, there should not be a second set of identical imported bookmarks.

Test notes

Brave Payments is not covered with this issue. That work is taking place in https://github.com/brave/brave-core/pull/736 (which fixes issue https://github.com/brave/brave-browser/issues/1215)

Description

brave-browser should recognize an optional argument, e.g. --upgrade-from-muon or --upgrade-from-browser-laptop, such that if the argument is provided, it should:

1. Check the system for an existing installation of browser-laptop.
2. If an existing installation is found, automatically import all supported data types from it silently and without user interaction.
3. Allow startup to continue.

We may also want to:

1. Automatically shut down or restart the browser once the import is complete. This could be the default behavior, or optionally triggered by an additional argument (e.g. --quit-after-import).
2. We should consider additionally checking to see if browser-laptop is the user’s current default browser, and only auto-import if it is.
   • For example, if I used browser-laptop for a few weeks last year, then switched to a different browser up until the present moment when I’ve decided to give brave-browser a try, I might be confused/unenthused if a bunch of out-of-date browsing data is automatically included with my first-run experience.

[bsclifton]

@srirambv you’ll get a chance to try that with the browser-laptop release, but as soon as brave-core is launched, browser-laptop quits

[davidtemkin]

When we auto-import from Muon following an upgrade, that is a version upgrade from a user POV. It’s like going from Chrome 69 to Chrome 70, except that there are, ahem, substantial changes. But the process we are modeling is that of upgrading a browser to the latest version, not that of installing a new browser and importing from a pre-existing browser. So the expectation is that a user’s data will be carried over.

A manual download, I think, is different. I don’t think we’d want to auto-import from any browser (Muon or other) when a user has manually downloaded/installed brave core. In that case, they need to decide what to do, as the process we are modeling in that case is one of installing a new browser. In that situation, it isn’t a given that they’d want to import from Muon, or from their default browser, or from any browser.