On Android, Chromium does not support automatic reconnection. The user
must manually pair the device after every reboot in order for
fastboot.js to reconnect to it. Unfortunately, this requires the user of
the library to get involved because USB device connction requests are
only allowed as the result of explicit user action, so we need to add a
reconnect request callback for the user to handle.
Some of the API and paths have changed, so this needs to be updated
accordingly. The most prominent change is the removal of BlobStore and
downloading support from fastboot.js, because a fastboot library should
not be responsible for downloading files.
