devtools: Make it possible to retrieve all cookies

This patch adds a new "global" mode to the Network.getCookies command
which allows retrieving all cookies in the browser cookie jar instead of
just the cookies for the current URL.

BUG=668932,166637

Review-Url: https://codereview.chromium.org/2554293002
Cr-Commit-Position: refs/heads/master@{#437246}
5 files changed