Fix: Correctly revoke objectURL for print blob in office viewer

[jeremypress]

Original fix here: #444
feeling the pain of repeated code

[pramodsum]

Is there any way we can consolidate this revoke logic amongst viewers so we won't run into an issue like this again?

[tonyjin]

@pramodsum: #62

We tabled that due to complications, but may be worth revisiting.

[jeremypress]

I don't think it would be worth it to just abstract the printURL without doing the rest, which ended up being pretty messy the first time I tried.