Revert 174956 "Oilpan: Move ThreadableWebSocketChannelClientWrap..."

This CL broke worker-reload-repeated.html in oilpan bots.

> Oilpan: Move ThreadableWebSocketChannelClientWrapper to Oilpan's heap
> 
> This is a preparation for moving WebSocketChannelClient to the heap.
> 
> This CL adds a template specialization to CrossThreadCopier.h so that ThreadableWebSocketChannelClientWrapper* can be passed to createCallbackTask().
> 
> BUG=340522
> 
> Review URL: https://codereview.chromium.org/267323004

TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/309503013

git-svn-id: svn://svn.chromium.org/blink/trunk@175242 bbb929c8-8fbe-4397-9dbb-9b2b20218538