[parser] Add convenient Print function for debugging.

src/parsing/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 6983 matching lines @@
     try_block->statements()->Add(loop, zone);
 
     FinalizeIteratorUse(var_completion, closing_condition, loop->iterator(),
                         try_block, target);
     final_loop = target;
   }
 
   return final_loop;
 }
 
+#ifdef DEBUG
+void Parser::Print(AstNode* node) {
+  ast_value_factory()->Internalize(Isolate::Current());
+  node->Print(Isolate::Current());
+}
+#endif  // DEBUG
 
 }  // namespace internal
 }  // namespace v8