Fall back to US regulatory label if the label cannot be found using the device region code.
Fall back to US regulatory label if the label cannot be found
using the device region code.

BUG=511018
R=dbeam@chromium.org
TEST=Alt+F2 and input below. Label should always be shown in chrome://help.

vpd -s region=us # Set region to US
dump_vpd_log --clean -force && reboot

vpd -s region=zz # Set bogus region
dump_vpd_log --clean -force && reboot

vpd -d region # Delete region code
dump_vpd_log --clean -force && reboot

Review URL: https://codereview.chromium.org/1303973003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#344704}

ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend