Bug 1084333. Part 2 - Add proprietes handling to BaseWindow. r=aeftimie, r=amatei, r=hskupin

--HG--
branch : mozilla-beta
extra : transplant_source : %23v%10%E3%00k%80%D7q%02%89%8D%DE%85%D2%F0%5D%E4%87%12
Bug 1084333 - Fix message from property to entity r=aeftimie r=amatei

--HG--
branch : mozilla-beta
extra : transplant_source : 4%F0%40r%0B%C7%EE1%12%E7%AF%FE%608l%0A%86%BB%5D%3F