Asynchronously obtains the OAuth 2.0 access token for source along with its expiry in seconds from the current time (or 0 if
unknown).
When the operation is finished, callback will be called. You can then call
get_access_token.end to get the result of the operation.
| this | |
| source |
an Source |
| cancellable |
optional Cancellable object, or null |
| callback |
a TaskReadyCallback to call when the request is satisfied |
| user_data |
data to pass to the callback function |