Test for WebSocketJob being deleted on the stack

      SocketStreamDispatcherHost can delete the WebSocketJob while it is still
on the stack. Add tests to ensure that WebSocketJob does not attempt to
access its own members after being deleted.

Also fix two cases where WebSocketJob attempted to access its members after
being deleted.

BUG=358038
TEST=net_unittests --gtest_filter=WebSocketJobDeleteTest*

Review URL: https://codereview.chromium.org/221833002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261707 0039d316-1c4b-4281-b951-d872f2087c98