cannot
even begin executing until Google Maps has fully loaded, on every
single page load, for every user. Only one screen in the whole app
renders a GoogleMap on web (screens/field_mapping_screen.dart;
market_prices_screen.dart deliberately uses OpenStreetMap under
kIsWeb), so that cost was being paid by everyone to benefit almost
no one — worst of all for the rural, low-bandwidth users this app
exists for, where 315 KB of blocking script is measured in seconds.
`defer` keeps the one guarantee google_maps_flutter_web needs — the
script still executes before DOMContentLoaded, in document order —
while taking it off the parser's critical path. There is no race
with Field Mapping: reaching that screen requires Flutter to have
booted at all, which means main.dart.js (1.9 MB brotli) plus the
CanvasKit runtime plus the asset fonts have all already loaded, and
every one of those is larger than this file.
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