Avoid using !OS() constructs.

Source/web/EditorClientImpl.cpp

 /*
  * Copyright (C) 2006, 2007 Apple, Inc.  All rights reserved.
  * Copyright (C) 2012 Google, Inc.  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
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 751 matching lines @@
 
 bool EditorClientImpl::spellingUIIsShowing()
 {
     if (m_webView->spellCheckClient())
         return m_webView->spellCheckClient()->isShowingSpellingUI();
     return false;
 }
 
 bool EditorClientImpl::supportsGlobalSelection()
 {
-#if OS(POSIX) && !OS(MACOSX)
+#if OS(WIN) || OS(MACOSX)
+    return false;
+#else
     return true;
-#else
-    return false;
 #endif
 }
 
 void EditorClientImpl::willSetInputMethodState()
 {
     if (m_webView->client())
         m_webView->client()->resetInputMethod();
 }
 
 } // namesace WebKit