IsolatedWorldCSP: Enforce CSP checks for websockets in isolated worlds.

Enforce CSP checks for websockets in isolated worlds. Also add tests for
websocket usage in isolated worlds and its interaction with CSP.

Since the IsolatedWorldCSP feature is disabled by default, this CL will cause
the CSP check to use an empty CSP instead of just bypassing the CSP checks for
isolated worlds. In practice, this should cause no behavior change.

BUG=896041

Change-Id: If13ea1a03591397970884e523255c85a265c8a53
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1616946
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661413}
5 files changed