I'll try to give a generic answer for Google Drive (disclosure: I work for Google, but not on Drive), Dropbox, Microsoft OneDrive, etc:
I would be conservative and not try this, unless I'm okay with risking data loss. These sync tools behave differently from from HFS+.
For example, Dropbox doesn't support symlinks. Put a file in Dropbox, and a symlink to it, and you'll end up with two copies of the file. This is different from a symlink, obviously — if you update the file, the changes don't reflect in the symlink, because it's no longer a symlink. This difference can break Lightroom and corrupt your library, if it uses symlinks and expect them to work the way symlinks do.
Symlinks are just one example. There are also other areas where Google Drive and Dropbox could be different from HFS+: hard links, aliases, resource forks, extended attributes, path length limits or disallowed characters, and so on.
If you're thinking about doing a test, you can't be sure that everything will work fine in the future if it works fine now. Maybe there's latent corruption in the library that's not visible yet, and will show up one day? Unless you've tested all the code paths in the Lightroom code, you can't be sure.
Drive and friends are for storing individual files, like Word documents. They are not safe for storing entire libraries like Lightroom, iPhoto, iTunes, etc.