Enable various bits and pieces of Content Security Policy Level 2.

Intent to Ship: https://groups.google.com/a/chromium.org/d/msg/blink-dev/wToP6b04zVE/imuPatGy3awJ

BUG=417610

Review URL: https://codereview.chromium.org/611243002

git-svn-id: svn://svn.chromium.org/blink/trunk@182899 bbb929c8-8fbe-4397-9dbb-9b2b20218538