Prevent deadlock in CookieSettings

Prevent deadlock If a CookieSettings::Observer calls
CookieSettings::ShouldBlockThirdPartyCookies() while being updated.

Bug: 967668
Change-Id: I5b769bc737fbed53f814865561395e6d7b85c6d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1667115
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671634}
2 files changed