Need an IP Range for google's CDN to set up a firewall

Their ASN is 15169; just have to look up the BGP table.

The answer is way more complicated than ASN 15169. First Google has more than one ASN:

15169 Google Inc.
16591 Google Fiber Inc.
36039 Google Inc.
36040 Google Inc.
36384 Google Incorporated
36492 Google, Inc.
41264 Google Switzerland GmbH

Second, Google, Akamai, etc use IP ranges of their partner ASNs to host content. So if you are a Time Warner customer, you may see Google CDN content coming from a server close to you that has an IP associated with Time Warner (via ASN) and not Google.

After all the whole point of CDNs is to distribute content efficiently.