Except if Google decided to drop their certs, what Synmantec going to do? Sue? Google could be sued for leaving known insecure certs in Chrome.
Also, and most critically, it's musical chairs between cloud and security companies. If Symantec came to Google to complain it's likely they'd go straight to VPs who used to work with them and get special treatment.
Hence the call to use notaries. Let's avoid the whole buddy network.