Google cloud's ssh command lets you pass standard ssh flags. To, for example, forward local port 8088 to port 8088 on a vm instance, all you need to do is:
gcloud compute ssh --ssh-flag="-L 8088:localhost:8088" --zone "us-central1-b" "example_instance_name"
Now browsing to localhost:8088 works as it would with standard ssh.
Thank you