Tests that 'BlockedByClient' network interception is executed with blockedReason set to 'inspector' (=devtools).
http://127.0.0.1:8000/inspector-protocol/network/resources/page-with-subresource.html
 1 - request will be sent
 2 - continuing to load
http://127.0.0.1:8000/inspector-protocol/network/resources/to-be-blocked.html
 1 - request will be sent
 2 - blocking
 3 - loading failed, blockedReason = inspector
http://127.0.0.1:8000/inspector-protocol/network/resources/to-be-blocked.jpg
 1 - request will be sent
 2 - blocking
 3 - loading failed, blockedReason = inspector