WebSocket should stop resuming when suspended.

WebSocket::resume starts a timer which does the actual resume work when fired.
WebSocket::suspend must stop the timer in case it is called while the
timer is active.

BUG=NONE
R=tyoshino

Review URL: https://codereview.chromium.org/330253002

git-svn-id: svn://svn.chromium.org/blink/trunk@176283 bbb929c8-8fbe-4397-9dbb-9b2b20218538