Specifically:
* Removed unused cookie_store.h include from chrome/browser/net
  and chrome/browser/safe_browsing.
* Switched content/public/test/browser_test_utils.cc over to Mojo accesses
  to cookies.
* The above required making the static CookieStore::BuildCookieLine
  available instead on CanonicalCookie (which is visible to Mojo clients
  when CookieStore is not).

Bug: 721395
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.linux:linux_site_isolation;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I8565fa795a48996774bd2d1aca21763dc31af3e8
Reviewed-on: https://chromium-review.googlesource.com/764944


Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Helen Li <xunjieli@chromium.org>
Commit-Queue: Randy Smith <rdsmith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516139}