Improving direction-based selection strategy.

Source/core/editing/VisibleSelection.cpp

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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 575 matching lines @@
         m_start = base;
         m_end = extent;
     } else {
         m_start = extent;
         m_end = base;
     }
     m_selectionType = base == extent ? CaretSelection : RangeSelection;
     didChange();
 }
 
+void VisibleSelection::setWithoutValidation(const Position& base, const Position& extent, const Position& start, const Position& end)
+{
+    ASSERT(!base.isNull());
+    ASSERT(!extent.isNull());
+    ASSERT(!start.isNull());
+    ASSERT(!end.isNull());
+    ASSERT(m_affinity == DOWNSTREAM);
+    ASSERT(comparePositions(start, end) <= 0);
+    m_base = base;
+    m_extent = extent;
+    m_baseIsFirst = comparePositions(base, extent) <= 0;
+    m_start = start;
+    m_end = end;
+    m_selectionType = base == extent ? CaretSelection : RangeSelection;
+    didChange();
+}
+
 static Position adjustPositionForEnd(const Position& currentPosition, Node* startContainerNode)
 {
     TreeScope& treeScope = startContainerNode->treeScope();
 
     ASSERT(currentPosition.containerNode()->treeScope() != treeScope);
 
     if (Node* ancestor = treeScope.ancestorInThisScope(currentPosition.containerNode())) {
         if (ancestor->contains(startContainerNode))
             return positionAfterNode(ancestor);
         return positionBeforeNode(ancestor);
@@ skipping 316 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const blink::VisibleSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif