JavaScript: add missing MessageEvent properties.

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@8782 5f5364db-9458-4db8-a492-e30667be6df6
Small performance enhancement, thanks to Ronald

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@8783 5f5364db-9458-4db8-a492-e30667be6df6
unused method removed

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@8784 5f5364db-9458-4db8-a492-e30667be6df6
add ff24 to our statistics

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@8785 5f5364db-9458-4db8-a492-e30667be6df6