[WebSocket] Do nothing for connect() if initialization has failed.

m_syncHelper will be 0 if initialize() fails. connect() must just return
with false in such case.

BUG=368329

Review URL: https://codereview.chromium.org/266483003

git-svn-id: svn://svn.chromium.org/blink/trunk@172973 bbb929c8-8fbe-4397-9dbb-9b2b20218538