addMessageToConsole now takes two additional parameters to specify the
message source (HTML, JS, CSS, XML) and level (error, warning, log). To
maintain our old behavior, all current messages were given
JSMessageSource and ErrorMessageLevel parameters. Messages matching
these characteristics are passed up to the ChromeClient.

Reviewed by Hyatt.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@21706 268f45cc-cd09-0410-ab3c-d52691b4dbfc