Bug fix: toPositionInComposedTree should treat positions with shadow roots

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 1393 matching lines @@
         return PositionInComposedTree();
 
     PositionInComposedTree position;
     if (pos.anchorType() == Position::PositionIsOffsetInAnchor) {
         Node* anchor = pos.anchorNode();
         if (anchor->offsetInCharacters())
             return PositionInComposedTree(anchor, pos.computeOffsetInContainerNode(), PositionInComposedTree::PositionIsOffsetInAnchor);
         ASSERT(!isActiveInsertionPoint(*anchor));
         int offset = pos.computeOffsetInContainerNode();
         Node* child = NodeTraversal::childAt(*anchor, offset);
-        if (!child)
+        if (!child) {
+            if (anchor->isShadowRoot())
+                return PositionInComposedTree(anchor->shadowHost(), PositionInComposedTree::PositionIsAfterChildren);
             return PositionInComposedTree(anchor, PositionInComposedTree::PositionIsAfterChildren);
+        }
         child->updateDistribution();
-        if (isActiveInsertionPoint(*child))
+        if (isActiveInsertionPoint(*child)) {
+            if (anchor->isShadowRoot())
+                return PositionInComposedTree(anchor->shadowHost(), offset, PositionInComposedTree::PositionIsOffsetInAnchor);
             return PositionInComposedTree(anchor, offset, PositionInComposedTree::PositionIsOffsetInAnchor);
+        }
         return PositionInComposedTree(ComposedTreeTraversal::parent(*child), ComposedTreeTraversal::index(*child), PositionInComposedTree::PositionIsOffsetInAnchor);
     }
 
     return PositionInComposedTree(pos.anchorNode(), static_cast<PositionInComposedTree::AnchorType>(pos.anchorType()));
 }
 
 Position toPositionInDOMTree(const PositionInComposedTree& position)
 {
     if (position.isNull())
         return Position();
@@ skipping 110 matching lines @@
 
 void showTree(const blink::Position* pos)
 {
     if (pos)
         pos->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree for (nil)\n");
 }
 
 #endif