In CA websites are already required to respect the opt-out setting implemented in the Global Privacy Control [1] extension. It's basically the same thing as do-not-track but starting from a clean slate so that the meaning of the setting in law is clearly defined.
This bill basically allows the regulator to make sure everyone in CA gets this extension automatically.
it says Browsers must send an opt-out signal.
Browsers have already had a do-not-track setting, and websites universally* ignored it.
* 99%