Oilpan: Move WebSocketChannel to oilpan's heap

This CL moves WebSocketChannel's hierarchy to Oilpan's heap.

This CL makes WebSocketChannel "RefCounted"GarbageCollected to support manual ref/deref in MainThreadWebSocketChannelImpl. It's possible to remove these ref/deref, but it wouldn't be much worth doing since MainThreadWebSocketChannelImpl is going to be removed in the near future.

BUG=340522

Review URL: https://codereview.chromium.org/262733013

git-svn-id: svn://svn.chromium.org/blink/trunk@173302 bbb929c8-8fbe-4397-9dbb-9b2b20218538