Re-land http://codereview.chromium.org/7831056/ and http://codereview.chromium.org/7833042/ .

Re-land http://codereview.chromium.org/7831056/ and http://codereview.chromium.org/7833042/ .

Finalize a CL originally by departed intern ycxiao@ that detaches the loading of cookies from the IO thread.

They are now loaded on the DB thread. Cookie operations received in the meantime are queued and executed, on the IO thread, in the order they were received, when loading completes.

A few straggler clients are updated to use the asynchronous CookieStore/CookieMonster API as part of this CL, as the synchronous API is removed.

This entire CL has been previously reviewed by the appropriate owners, however an error was made during the submit.

BUG=68657
TEST=net_unittests / DeferredCookieTaskTest.* and CookieMonsterTest.*
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=100415