[cast_channel] Make CastMessageHandler a CastSocket::Observer instead of CastTransport::Delegate

components/cast_channel/cast_test_util.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/cast_channel/cast_test_util.h"
 
 #include <utility>
 
 #include "net/base/ip_address.h"
 
 namespace cast_channel {
 
 MockCastTransport::MockCastTransport() {}
 MockCastTransport::~MockCastTransport() {}
 
 CastTransport::Delegate* MockCastTransport::current_delegate() const {
   CHECK(delegate_);
   return delegate_.get();
 }
 
 void MockCastTransport::SetReadDelegate(
     std::unique_ptr<CastTransport::Delegate> delegate) {
   delegate_ = std::move(delegate);
 }
 
 MockCastTransportDelegate::MockCastTransportDelegate() {}
 MockCastTransportDelegate::~MockCastTransportDelegate() {}
 
+MockCastSocketObserver::MockCastSocketObserver() {}
+MockCastSocketObserver::~MockCastSocketObserver() {}
+
 MockCastSocket::MockCastSocket() : mock_transport_(new MockCastTransport()) {}
 MockCastSocket::~MockCastSocket() {}
 
 net::IPEndPoint CreateIPEndPointForTest() {
   return net::IPEndPoint(net::IPAddress(192, 168, 1, 1), 8009);
 }
 
 }  // namespace cast_channel