[Editing][DOM][CodeHealth] Make Node::isContentEditable and Node::isRichEditable global functions.

third_party/WebKit/Source/core/editing/commands/DeleteFromTextNodeCommand.cpp

 /*
  * Copyright (C) 2005, 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 28 matching lines @@
 {
     DCHECK(m_node);
     DCHECK_LE(m_offset, m_node->length());
     DCHECK_LE(m_offset + m_count, m_node->length());
 }
 
 void DeleteFromTextNodeCommand::doApply(EditingState*)
 {
     DCHECK(m_node);
 
-    if (!m_node->isContentEditable())
+    if (!isContentEditable(*m_node))
         return;
 
     TrackExceptionState exceptionState;
     m_text = m_node->substringData(m_offset, m_count, exceptionState);
     if (exceptionState.hadException())
         return;
 
     m_node->deleteData(m_offset, m_count, exceptionState);
     m_node->document().updateStyleAndLayout();
 }
 
 void DeleteFromTextNodeCommand::doUnapply()
 {
     DCHECK(m_node);
 
     if (!m_node->hasEditableStyle())
         return;
 
     m_node->insertData(m_offset, m_text, IGNORE_EXCEPTION);
     m_node->document().updateStyleAndLayout();
 }
 
 DEFINE_TRACE(DeleteFromTextNodeCommand)
 {
     visitor->trace(m_node);
     SimpleEditCommand::trace(visitor);
 }
 
 } // namespace blink