Load the given content string for the URI content_uri.
This allows clients to display page-loading errors in the WebView itself. When this method is called from load_failed signal to show an error page, then the back-forward list is maintained appropriately. For everything else this method works the same way as load_html.
| this |
a WebView |
| content |
the new content to display as the main page of the this |
| content_uri |
the URI for the alternate page content |
| base_uri |
the base URI for relative locations or null |