improve synchronization
Issue 1530


git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@8811 5f5364db-9458-4db8-a492-e30667be6df6
improve synchronization

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@8812 5f5364db-9458-4db8-a492-e30667be6df6