I don't feel qualified to answer your question, though if I were to make a guess, I wouldn't expect them to be put off by refusal. Assuming Google behaves at least somewhat rationally, they should at this point have an estimate of your value as an employee and it doesn't seem like your current salary would provide much additional information on that.

So, the question is, to what extent Google behaves rationally. This ties to something that I always wonder whenever I read salary negotiation advice. What is the specific mechanism by which disclosing current salary can hurt you? Yes, anchoring, obviously. But who does it? Is the danger that the potential employer isn't behaving rationally after all and will anchor to the current salary, lowering the upper bound on what they're willing to offer? Or is the danger primarily that anchoring will undermine your confidence and willingness to demand more (and if you felt sufficiently entitled, it wouldn't hurt you at all)?