load_html
Description:
Load the given content string with the specified base_uri.
If base_uri is not null, relative URLs in the content will be resolved against 
      base_uri and absolute local paths must be children of the base_uri. For security reasons absolute local paths that are
       not children of base_uri will cause the web process to terminate. If you need to include URLs in content that are 
      local paths in a different directory than base_uri you can build a data URI for them. When base_uri is 
      null, it defaults to "about:blank". The mime type of the document will be "text/html". You can monitor the 
      load operation by connecting to load_changed signal.
Parameters:
| this | a WebView | 
| content | The HTML string to load | 
| base_uri | The base URI for relative locations or null |