Oilpan: fix WebSockets unit test GC plugin failure.

Source/modules/websockets/NewWebSocketChannelImplTest.cpp

 // 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 "config.h"
 #include "modules/websockets/WebSocketChannel.h"
 
 #include "core/fileapi/Blob.h"
 #include "core/frame/ConsoleTypes.h"
 #include "core/testing/DummyPageHolder.h"
@@ skipping 43 matching lines @@
     MOCK_METHOD1(didReceiveMessage, void(const String&));
     virtual void didReceiveBinaryData(PassOwnPtr<Vector<char> > binaryData) OVERRIDE
     {
         didReceiveBinaryDataMock(*binaryData);
     }
     MOCK_METHOD1(didReceiveBinaryDataMock, void(const Vector<char>&));
     MOCK_METHOD0(didReceiveMessageError, void());
     MOCK_METHOD1(didConsumeBufferedAmount, void(unsigned long));
     MOCK_METHOD0(didStartClosingHandshake, void());
     MOCK_METHOD3(didClose, void(ClosingHandshakeCompletionStatus, unsigned short, const String&));
-    MOCK_METHOD1(trace, void(Visitor*));
+
+    virtual void trace(Visitor* visitor) OVERRIDE
+    {
+        WebSocketChannelClient::trace(visitor);
+    }
+
 };
 
 class MockWebSocketHandle : public blink::WebSocketHandle {
 public:
     static MockWebSocketHandle* create()
     {
         return new testing::StrictMock<MockWebSocketHandle>();
     }
 
     MockWebSocketHandle() { }
@@ skipping 652 matching lines @@
         EXPECT_CALL(*channelClient(), didReceiveMessageError());
         EXPECT_CALL(*channelClient(), didClose(WebSocketChannelClient::ClosingHandshakeIncomplete, WebSocketChannel::CloseEventCodeAbnormalClosure, String()));
     }
 
     channel()->fail("fail message from WebSocket", ErrorMessageLevel, "sourceURL", 1234);
 }
 
 } // namespace
 
 } // namespace WebCore