Ignore visibility when checking whether Position is editable or not at DeletetSelectionCommand

Source/core/editing/htmlediting.h

Index: Source/core/editing/htmlediting.h
diff --git a/Source/core/editing/htmlediting.h b/Source/core/editing/htmlediting.h
index bcc80193a7f9231053ded9a74c93a01975b417a5..d66d919f2cf91f0c0c94f9a2672e2f3f5bc3e50e 100644
--- a/Source/core/editing/htmlediting.h
+++ b/Source/core/editing/htmlediting.h
@@ -144,6 +144,8 @@ inline Position lastPositionInOrAfterNode(Node* node)
     return editingIgnoresContent(node) ? positionAfterNode(node) : lastPositionInNode(node);
 }
 
+Position lastEditablePositionBeforePositionInRoot(const Position&, Node*);
+
 // comparision functions on Position
 
 int comparePositions(const Position&, const Position&);