[WebSocket] Add extension attribute support

[WebSocket] Add extension attribute support
https://bugs.webkit.org/show_bug.cgi?id=78557

Source/WebCore:

Implement WebSocket "extensions" attribute that holds a list of
extension the server accepted. No change in behavior at this time
because we don't send any extension on handshake.

Reviewed by Kent Tamura.

No new tests. http/tests/websocket/tests/hybi/extensions.html checks the value of this attribute.

* websockets/ThreadableWebSocketChannel.h: Add extensions().
(ThreadableWebSocketChannel):
* websockets/ThreadableWebSocketChannelClientWrapper.cpp:
(WebCore::ThreadableWebSocketChannelClientWrapper::extensions): Added.
(WebCore):
(WebCore::ThreadableWebSocketChannelClientWrapper::setExtensions): Added.
* websockets/ThreadableWebSocketChannelClientWrapper.h:
(ThreadableWebSocketChannelClientWrapper):
* websockets/WebSocket.cpp: Added m_extensions member variable.
(WebCore::WebSocket::WebSocket):
(WebCore::WebSocket::extensions): Returns m_extensions.
* websockets/WebSocket.h:
* websockets/WebSocketChannel.cpp:
(WebCore::WebSocketChannel::extensions): Added.
(WebCore):
* websockets/WebSocketChannel.h:
(WebSocketChannel):
* websockets/WebSocketExtensionDispatcher.cpp:
(WebCore::WebSocketExtensionDispatcher::fail): Added.
(WebCore::WebSocketExtensionDispatcher::processHeaderValue): Stores accepted extensions.
(WebCore::WebSocketExtensionDispatcher::acceptedExtensions): Added.
(WebCore):
(WebCore::WebSocketExtensionDispatcher::acceptedExtensions): Added.
* websockets/WebSocketExtensionDispatcher.h:
(WebSocketExtensionDispatcher):
* websockets/WebSocketHandshake.cpp:
(WebCore::WebSocketHandshake::acceptedExtensions): Added.
(WebCore):
* websockets/WebSocketHandshake.h:
* websockets/WorkerThreadableWebSocketChannel.cpp:
(WebCore::WorkerThreadableWebSocketChannel::extensions): Added.
(WebCore):
(WebCore::workerContextDidConnect): Calls ThreadableWebSocketChannelClientWrapper::setExtensions().
(WebCore::WorkerThreadableWebSocketChannel::Peer::didConnect): Passes extensions as an argument.
* websockets/WorkerThreadableWebSocketChannel.h:
(WorkerThreadableWebSocketChannel):

Source/WebKit/chromium:

Add WebSocketExtensionDispatcher::acceptedExtensions() checks.

Reviewed by Kent Tamura.

* tests/WebSocketExtensionDispatcherTest.cpp:
(WebCore::TEST_F):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107769 268f45cc-cd09-0410-ab3c-d52691b4dbfc