This method will have no effect when the network service is out of process.  Individual NetworkContexts are configured to have or not have CookieStores when they're created anyways (As was the case with URLRequestContextBuilders, before actually).  With the network service, the method has no effect - doesn't look like it was doing anything before, anyways, as the only URLRequestContexts we were constructing all forced cookies to be enabled.

The SetDefaultCookiePolicyToBlock() call in the cloud print service (chrome/service/service_main.cc) does look to be useful, however, as the cloud print service just called URLRequestContextBuilder.Build() without setting any cookie options, which will get out an in-memory cookie store.  Fixing that not to create a cookie store should allow the call to be removed there, too, though.