How to leak information...unintentionally
You don't do chips, do you?
TSMC has several modes of operation. One where you pass off RTL to them and they do the synthesis, P&R, etc. This is the "handholding for newbie startups" mode. TSMC could, if it desired, change your logic and hide it from you since they also design the test patterns.
The other mode is where they take GDS2 (geometric trapezoids) and hand you back silicon. This is the one that serious companies use. In this case TSMC is practically locked out since they'd have to decompile the GDS, make changes, and hope like h*ll that they didn't change the test patterns you've already generated. The odds of this are infinitesimal on any practically sized SoC.
I expect Google is a serious company, with serious money to spend given that they are going to this extent for security so TSMC isn't a practical attack vector. Your better bet would be to corrupt one of Google's IP suppliers and try to inject a vulnerability there. I seriously doubt Google is designing the microcontroller, for example, so that's where I'd start if I wanted to corrupt this sequence, although you could do it on any of several IP blocks they use.