URLRequestJob calls URLRequest::Cancel when entering suspend mode.  The reason for this is that connections tend to be blackholed on network changes.

This can result in URLRequestJob signalling a read failure when there's no pending read, which is weird.  It also results in URLRequestJobs that are not going over the network failing when they shouldn't.

Before this issue is tackled, we should figure two things:
1)  Should QUIC requests be cancelled in this case?  It's unclear if QUIC recovers smoothly from this case or not.
2)  Should we change the error we're failing with?  Right now, we fail with ERR_ABORTED, which cancels top level navigations.  Seems like we should fail with ERR_NETWORK_SUSPENDED, and if Chrome wants to cancel the navigation instead of showing an error page in response, it's up to Chrome to do so, not the network stack.