[Service Worker Registration] Registered extension scheme to allow service workers

Service Workers require a secure origin, such as HTTPS.  chrome-extension:// pages are not HTTP/HTTPS, but are secure so this change becomes a necessary step to allow extensions to register a Service Worker.

"chrome-extension" is added as a scheme allowing service workers.

BUG=501569

Review URL: https://codereview.chromium.org/1211243010

Cr-Commit-Position: refs/heads/master@{#338708}
10 files changed