[GTK] Handle files being disallowed in DragDataGtk after 254380@main

https://bugs.webkit.org/show_bug.cgi?id=247359

Reviewed by Michael Catanzaro.

We need to do the same changes done in 254380@main for DragDataGtk.

* Source/WebCore/platform/gtk/DragDataGtk.cpp:
(WebCore::DragData::containsFiles const):
(WebCore::DragData::numberOfFiles const):
(WebCore::DragData::asFilenames const):

Canonical link: https://commits.webkit.org/256232@main

Source/WebCore/platform/gtk/DragDataGtk.cpp

@@ -1,4 +1,6 @@
 /*
+ *  Copyright (C) 2016 Igalia S.L.
+ *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ -33,16 +35,18 @@ bool DragData::containsColor() const
 
 bool DragData::containsFiles() const
 {
-    return m_platformDragData->hasFilenames();
+    return !m_disallowFileAccess && m_platformDragData->hasFilenames();
 }
 
 unsigned DragData::numberOfFiles() const
 {
-    return m_platformDragData->filenames().size();
+    return !m_disallowFileAccess ? m_platformDragData->filenames().size() : 0;
 }
 
 Vector<String> DragData::asFilenames() const
 {
+    if (m_disallowFileAccess)
+        return { };
     return m_platformDragData->filenames();
 }