Remove NewWebSocketChannelImpl::Resumer

Since WebSocketChannelClient methods in WebSocket can be called even if
it is suspended or stopped, we don't need Resumer any more.

BUG=302898
R=tyoshino

Review URL: https://codereview.chromium.org/38513003

git-svn-id: svn://svn.chromium.org/blink/trunk@160467 bbb929c8-8fbe-4397-9dbb-9b2b20218538