Refactored the abstraction layer to address prerendered pages on Safari 7 and a slightly leaky abstraction.

http://codereview.adblockplus.org/5464830253203456/

--HG--
extra : rebase_source : d4182bc0f8ff7cd20abe3fd7969c7b01580c63a0
extra : amend_source : 7a29e4ef25d692850cd29f6012d5e39a56f990d2
Simplified and removed memory leaks from code dealing with frames on Chrome.

http://codereview.adblockplus.org/5133931611422720/
Cleaned up code of background page proxy for Safari.

http://codereview.adblockplus.org/5670052883857408/
Convert region code to uppercase when generating translation file URL on Safari.

http://codereview.adblockplus.org/4871895371481088/