Fixing MediaTest#testAddSource to only compare the end of the src to the src that was set.  Some browsers automatically prepend the host path to the src file name.

Review at http://gwt-code-reviews.appspot.com/1427811


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10121 8db76d5a-ed1c-0410-87a9-c151d255dfc7