Userscripts on special documents should be tested

Userscripts on special documents should be tested
<https://bugs.webkit.org/show_bug.cgi?id=44725>

Reviewed by Dave Hyatt.

Add tests of user script injection in audio, image, plugin, and video documents.

* userscripts/user-script-audio-document.html: Added. Test injection of user scripts
    in an audio document.
* userscripts/user-script-audio-document-expected.txt: Added.
* userscripts/user-script-image-document.html: Added. Test injection of user scripts
    in an image document.
* userscripts/user-script-image-document-expected.txt: Added.
* userscripts/user-script-plugin-document.html: Added. Test injection of user scripts
    in a plugin document.
* userscripts/user-script-plugin-document-expected.txt: Added.
* userscripts/user-script-video-document.html: Added. Test injection of user scripts
    in a video document.
* userscripts/user-script-video-document-expected.txt: Added.

* userscripts/resources/abe.png: Copied from media/content/abe.png.
* userscripts/resources/counting.mp4: Copied from media/content/counting.mp4.
* userscripts/resources/test.wav: Copied from media/content/test.wav.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@66144 268f45cc-cd09-0410-ab3c-d52691b4dbfc