Merge "WebView: clarify CookieManager docs" am: 5844882671 am: d2243be46a

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1569302

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I130a75f2e07ccb592ec300fa69f729ab367cbd7d