Does this app use Google docs?
No. Google docs used to show you your bookmarks "virtually". They were read only and not updateable in any way. Google probably did this as a simple way to allow you to access your bookmarks from any other browser. The data itself is held elsewhere in the main sync database. Since Google revamped the Docs interface at the start of 2011, you can no longer view bookmarks in Google docs. I have yet to find another web-based way to see your Chrome bookmarks.
For CMarks to be able to access your Google docs, you would either need to provide it with an id or password or authorise a security request for the docs (or "writely") service. Without an id or password from you or approval to use your credentials, an Android app cannot access your Google docs anyway. And CMarks asks for neither. The only credential it asks for is "chromiumsync" which allows the app access to the main sync database as detailed above.
For CMarks to be able to access your Google docs, you would either need to provide it with an id or password or authorise a security request for the docs (or "writely") service. Without an id or password from you or approval to use your credentials, an Android app cannot access your Google docs anyway. And CMarks asks for neither. The only credential it asks for is "chromiumsync" which allows the app access to the main sync database as detailed above.