https://bugs.webkit.org/show_bug.cgi?id=92341

Reviewed by Anders Carlsson.

Send diagnostic messages when a media or plugin element loads or fails to load. Include in
the trace the media engine description, error code, or plugin mime type.

* html/HTMLEmbedElement.cpp:
(WebCore::HTMLEmbedElement::updateWidget): Send a diagnostic message.
* html/HTMLMediaElement.cpp:
(WebCore::stringForNetworkState): Added convenience function to stringify network states.
(WebCore::HTMLMediaElement::mediaLoadingFailed): Send a diagnostic message.
(WebCore::HTMLMediaElement::setReadyState): Send a diagnostic message.
* html/HTMLObjectElement.cpp:
(WebCore::HTMLObjectElement::updateWidget): Send a diagnostic message.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@123780 268f45cc-cd09-0410-ab3c-d52691b4dbfc