Delete the old WebSocket implementation.

The WebSocket implementation has moved to chrome. As it is stable now, let's
delete the old implementation.
This CL doesn't delete some platform/ and web/ classes, as some chromium-side
code depends on them.

BUG=423201
R=ricea@chromium.org

Review URL: https://codereview.chromium.org/639333003

git-svn-id: svn://svn.chromium.org/blink/trunk@183642 bbb929c8-8fbe-4397-9dbb-9b2b20218538