storage: bucket.makePublic(fd, cb) & bucket.makePrivate(fd, cb)

The web interface supports a shared-publicly checkbox (see screenshot below). We should support this functionality for easy-share links! BAM!

Something like this:

bucket.makePublic('filename.png', function(err, public_url) {
  console.log(public_url); // https://storage.googleapis.com/bucket-name/filename.png
}); // could also return file stat instead of public url for more info

bucket.makePrivate('filename.png', function(err, stat) {
  console.log(stat.acl); // [] (assuming acl is the ObjectAccessControls object here) 
});

Screenshot:

This should go into the write operation as previously suggested. ACL changes should succeed and fail with metadata/contents changes atomically.

Btw, in your use case, you can set bucket's default ACL to be publicly readable. https://developers.google.com/storage/docs/json_api/v1/defaultObjectAccessControls/insert (Developers Console has a screen to manage bucket ACL as well.) You dont have to set ACL for each individual file.

Most of the time, people create a separate bucket for public blobs.