JavaScript: fix Storage prototype properties.
Issue 1639

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@9658 5f5364db-9458-4db8-a492-e30667be6df6
Fixing build

git-svn-id: svn://svn.code.sf.net/p/htmlunit/code/trunk@9659 5f5364db-9458-4db8-a492-e30667be6df6