CSP: Dedicated workers always inherit policy.

Based on the discussion in https://github.com/w3c/webappsec-csp/issues/146,
we're dropping the distinct policy for dedicated workers; they will now always
inherit the policy of their responsible document (just like every other script
executing in that page's context).

Intent to Ship: https://groups.google.com/a/chromium.org/d/msg/blink-dev/npKDoKVOUAs/ogtlIFmLBAAJ

BUG=662930

Review-Url: https://codereview.chromium.org/2540983003
Cr-Commit-Position: refs/heads/master@{#458039}
17 files changed