Re-introduce printers for Node, Position, PositionAnchorType in GTest

Source/core/editing/Position.h

Index: Source/core/editing/Position.h
diff --git a/Source/core/editing/Position.h b/Source/core/editing/Position.h
index caa8e862bfa59c3173a3a7515b05cc9134e41fa1..5821c0576522f1c9571b583eeddb9975bfe7270a 100644
--- a/Source/core/editing/Position.h
+++ b/Source/core/editing/Position.h
@@ -390,6 +390,15 @@ inline PositionInComposedTree fromPositionInDOMTree<EditingInComposedTreeStrateg
     return toPositionInComposedTree(position);
 }
 
+// These printers are available only for testing in "webkit_unit_tests", and
+// implemented in "core/testing/CoreTestPrinters.cpp".
+std::ostream& operator<<(std::ostream&, const Node&);
+std::ostream& operator<<(std::ostream&, const Node*);
+
+std::ostream& operator<<(std::ostream&, PositionAnchorType);
+std::ostream& operator<<(std::ostream&, const Position&);
+std::ostream& operator<<(std::ostream&, const PositionInComposedTree&);
+
 } // namespace blink
 
 #ifndef NDEBUG