Chrome protects its Secure Preferences file with a per-installation HMAC seed stored at /tmp/chrome_pref_hash_seed.bin. Any external script that writes to extensions.settings without knowing this seed produces a MAC that Chrome rejects on startup, silently moving the bad entry into prefs.tracked_preferences_reset like a quarantine bucket. Your injection 'succeeds' but the extension never actually loads, and there's no error message to point you at the real cause.
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