Make user-select:none not to affect editability

Source/core/dom/Position.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2009 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 825 matching lines @@
             if ((o->isText() && boundingBoxLogicalHeight(o, toRenderText(o)->linesBoundingBox()))
                 || (o->isBox() && toRenderBox(o)->pixelSnappedLogicalHeight())
                 || (o->isRenderInline() && isEmptyInline(o) && boundingBoxLogicalHeight(o, toRenderInline(o)->linesBoundingBox())))
                 return true;
         }
     return false;
 }
 
 bool Position::nodeIsUserSelectNone(Node* node)
 {
-    return node && node->renderer() && node->renderer()->style()->userSelect() == SELECT_NONE;
+    return node && node->renderer() && node->renderer()->style()->userSelect() == SELECT_NONE && node->renderer()->style()->userModify() == READ_ONLY;
 }
 
 ContainerNode* Position::findParent(const Node* node)
 {
     return node->parentNode();
 }
 
 #if ENABLE(USERSELECT_ALL)
 bool Position::nodeIsUserSelectAll(const Node* node)
 {
@@ skipping 534 matching lines @@
     pos.showTreeForThis();
 }
 
 void showTree(const WebCore::Position* pos)
 {
     if (pos)
         pos->showTreeForThis();
 }
 
 #endif