GitLab

* Converts SystemCookieStore to Async
* Add Async functions to NSHTTPSystemCookieStore and keep the synchronous
functions.
* Move creation time management to systemCookieStore.
* Update cookie_store_ios_presistent_unittest &
cookie_store_ios_unittests to account for SystemCookieStore changes
* (As CookieStoreIOS is using systemCookieStore internally).

Another CL is in progress to add WKSystemCookieStore & unit_tests for
systemCookieStore (to handle async methods) with template for both
NSHTTP & WK systemCookieStore.

Bug: 759229, 759227, 767948
Change-Id: If5e1fdb8d6424085d5212a3ea867968642db554f
Reviewed-on: https://chromium-review.googlesource.com/700818Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mohammad Refaat <mrefaat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506549}