CSP: 'violated-directive' should match 'effective-directive'.

In [1], mikispag@ noted that we're currently returning the entire
text of the violated directive, including its source list, etc. This
information is replicated in the report via the 'original-policy'
property, and CSP3 defines both 'violated-directive' and
'effective-directive' to contain the same data.

This patch changes our implementation in line with the spec.

[1]: https://github.com/w3c/web-platform-tests/pull/4020


Review-Url: https://codereview.chromium.org/2447003002
Cr-Commit-Position: refs/heads/master@{#427634}
30 files changed