Introduce a WebSocketChannel class for the new WebSocket implementation.

We are implementing the new WebSocket implementation. 
This CL introduces a WebSocketChannel derived class for the new WebSocket
implementation.
NewWebSocketChannelImpl implements WebSocketHandleClient and uses
WebSocketHandle to communicate with chrome side implementation.
NewWebSocketChannelImpl does not support many features such as logging,
blob and so on yet. They will be supported in the future.

This class will be tested when content and chrome implementation is done. 
Currently this cl doesn't change any behavior because nobody uses the classes yet. 

BUG=275459
R=abarth, tyoshino

Review URL: https://chromiumcodereview.appspot.com/23606006

git-svn-id: svn://svn.chromium.org/blink/trunk@156910 bbb929c8-8fbe-4397-9dbb-9b2b20218538