[parser] Add convenient Print function for debugging.

R=rossberg@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2127833002
Cr-Commit-Position: refs/heads/master@{#37554}

src/parsing/parser.cc

@@ -7001,6 +7001,12 @@ Statement* ParserTraits::FinalizeForOfStatement(ForOfStatement* loop, int pos) {
   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

src/parsing/parser.h

@@ -1117,6 +1117,10 @@ class Parser : public ParserBase<ParserTraits> {
   HistogramTimer* pre_parse_timer_;
 
   bool parsing_on_main_thread_;
+
+#ifdef DEBUG
+  void Print(AstNode* node);
+#endif  // DEBUG
 };