This tests the interaction between Content Security Policy and
Signature-based Subresource Integrity.

Bug: 753349
Change-Id: I45e269e43792d0e2893e5e26a7431ef64a304b84
Reviewed-on: https://chromium-review.googlesource.com/631723
Commit-Queue: Daniel Vogelheim <[email protected]>
Reviewed-by: Mike West <[email protected]>
Cr-Commit-Position: refs/heads/master@{#497362}