Fix unused functions warnings on Linux.

Source/core/page/DragController.cpp

 /*
  * Copyright (C) 2007, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Google Inc.
  *
  * 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
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 74 matching lines @@
 
 namespace WebCore {
 
 const int DragController::DragIconRightInset = 7;
 const int DragController::DragIconBottomInset = 3;
 
 static const int MaxOriginalImageArea = 1500 * 1500;
 static const int LinkDragBorderInset = 2;
 static const float DragImageAlpha = 0.75f;
 
+#if !ASSERT_DISABLED
 static bool dragTypeIsValid(DragSourceAction action)
 {
     switch (action) {
     case DragSourceActionDHTML:
     case DragSourceActionImage:
     case DragSourceActionLink:
     case DragSourceActionSelection:
         return true;
     case DragSourceActionNone:
         return false;
     }
     // Make sure MSVC doesn't complain that not all control paths return a value.
     return false;
 }
+#endif
 
 static PlatformMouseEvent createMouseEvent(DragData* dragData)
 {
     bool shiftKey, ctrlKey, altKey, metaKey;
     shiftKey = ctrlKey = altKey = metaKey = false;
     int keyState = dragData->modifierKeyState();
     shiftKey = static_cast<bool>(keyState & PlatformEvent::ShiftKey);
     ctrlKey = static_cast<bool>(keyState & PlatformEvent::CtrlKey);
     altKey = static_cast<bool>(keyState & PlatformEvent::AltKey);
     metaKey = static_cast<bool>(keyState & PlatformEvent::MetaKey);
@@ skipping 807 matching lines @@
     return false;
 #endif
 }
 
 void DragController::cleanupAfterSystemDrag()
 {
 }
 
 } // namespace WebCore