Block WebSocket connection to insecure server from secure page.

The W3C WebSocket API specifies that the browser must throw an SecurityError
exception if the requested URL is insecure and the origin is secure.

BUG=85271
R=tyoshino, abarth

Review URL: https://codereview.chromium.org/143763002

git-svn-id: svn://svn.chromium.org/blink/trunk@165922 bbb929c8-8fbe-4397-9dbb-9b2b20218538