Remove dead ContextMenu code from Blink core

Source/core/loader/EmptyClients.h

 /*
  * Copyright (C) 2006 Eric Seidel (eric@webkit.org)
  * Copyright (C) 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 337 matching lines @@
 
 private:
     EmptyTextCheckerClient m_textCheckerClient;
 };
 
 class EmptyContextMenuClient : public ContextMenuClient {
     WTF_MAKE_NONCOPYABLE(EmptyContextMenuClient); WTF_MAKE_FAST_ALLOCATED;
 public:
     EmptyContextMenuClient() { }
     virtual ~EmptyContextMenuClient() {  }
-    virtual PassOwnPtr<ContextMenu> customizeMenu(PassOwnPtr<ContextMenu>) OVERRIDE;
+    virtual void showContextMenu(const ContextMenu*) OVERRIDE { }
 };
 
 class EmptyDragClient : public DragClient {
     WTF_MAKE_NONCOPYABLE(EmptyDragClient); WTF_MAKE_FAST_ALLOCATED;
 public:
     EmptyDragClient() { }
     virtual ~EmptyDragClient() {}
     virtual DragDestinationAction actionMaskForDrag(DragData*) OVERRIDE { return DragDestinationActionNone; }
     virtual void startDrag(DragImageRef, const IntPoint&, const IntPoint&, Clipboard*, Frame*, bool) OVERRIDE { }
 };
@@ skipping 37 matching lines @@
     virtual int forwardListCount() OVERRIDE { return 0; }
     virtual bool isActive() OVERRIDE { return false; }
     virtual void close() OVERRIDE { }
 };
 
 void fillWithEmptyClients(Page::PageClients&);
 
 }
 
 #endif // EmptyClients_h