Google Drive XBlock - Fake PR for review purposes, do not merge!

@martynjames Created this PR for the review. 

Btw for the future, it's easier to create this when the first commit is empty. Also, if we want to review a series of PRs at once instead of individual PRs, it would be easier to merge the individual PRs in a branch which isn't master, and then create a PR from that branch into master when it's ready -- this way we don't need "fake" PRs at all, they represent the actual review workflow.
You can pass the event name as a parameter, that would allow to factor these methods and avoid having as many as there are event types. See https://github.com/edx-solutions/xblock-utils/blob/master/xblockutils/publish_event.py