This patch includes:
- changes to WebRequest.jsm to always default to only merge the CSP headers returned by MV3 extensions
- changes to the test_ext_webRequest_mergecsp.js xpcshell test to cover the behavior expected
with MV3 extensions and combinations of both MV2 and MV3 extensions changing CSP headers
for the same intercepted web request.
For MV3 extensions we would prefer a more explicit and predictable way for the
extensions to be allowed to replace the CSP header, instead of keeping the same
unpredictable and implicit one that we currently support for MV2 extensions.
Differential Revision: https://phabricator.services.mozilla.com/D154983
5549205044