Asynchronously run the script from resource.
Asynchronously run the script from resource in the context of the current page in this.
When the operation is finished, callback will be called. You can then call
run_javascript_from_gresource.end to get the result of the operation.
| this |
a WebView |
| resource |
the location of the resource to load |
| cancellable |
a Cancellable or null to ignore |
| callback |
a TaskReadyCallback to call when the script finished |
| user_data |
the data to pass to callback function |